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input/code.cpp: In function 'int main()':
input/code.cpp:22:40: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'll' {aka 'long long int'} [-Wsign-compare]
   22 | #define fr(i,a,b) for (size_t i = a; i < b; i++)
      |                                        ^
input/code.cpp:67:3: note: in expansion of macro 'fr'
   67 |   fr(i, 0, wide - 1) {
      |   ^~
input/code.cpp:22:40: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'll' {aka 'long long int'} [-Wsign-compare]
   22 | #define fr(i,a,b) for (size_t i = a; i < b; i++)
      |                                        ^
input/code.cpp:73:3: note: in expansion of macro 'fr'
   73 |   fr(i, 0, tall - 1) {
      |   ^~
input/code.cpp:22:40: warning: comparison of integer expressions of different signedness: 'size_t' {aka 'long unsigned int'} and 'll' {aka 'long long int'} [-Wsign-compare]
   22 | #define fr(i,a,b) for (...

// clang-format off
#include <bits/stdc++.h>
using namespace std;
#ifdef DO_DBG
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { os << '{'; string sep; for (const T &x : v) os << sep << x, sep = ", "; return os << '}'; }
void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cerr << ' ' << H; dbg_out(T...); }
#define dbg(...) cerr << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__)
#define dout cerr
#define debug true
#else
#define dbg(...)
#define dout if (0) cerr
#define debug false
#endif
typedef long long ll; typedef unsigned long long ull; typedef long double ld;
template <typename T> using v = vector<T>; template <typename T> using us = unordered_set<T>; template <typename K, typename V> using p = pair<K,V>;
template <typename K, typename V> using um = unordered_map<K, V>; template <typename K, typename V> using p = pair<K, V>;
template <typename T> using pq = priority_queue<T>; template <typename T> using nl = numeric_limits<T>; template <typename T> using il = initializer_list<T>;
constexpr int MOD = 1e9 + 7; constexpr int INF = 1e9; constexpr ld EPS = 1e-9;
#define fr(i,a,b) for (size_t i = a; i < b; i++)
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); cin.exceptions(cin.failbit);
#define frr(i,a,b) for (size_t i = b-1; i >= a; i--)
#define frs(i,a,b) for (ll i = a; i < b; i++)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define sq(x) ((x) * (x))
template <typename... Args> void read(Args&... args) { ((cin >> args), ...); }
#define d(...) int __VA_ARGS__; read(__VA_ARGS__);
#define dll(...) ll __VA_ARGS__; read(__VA_ARGS__);
#define dv(x, n) vector<int> x(n); for (int i = 0; i < n; i++) cin >> x[i];
#define dvll(x, n) vector<long long> x(n); for (int i = 0; i < n; i++) cin >> x[i];
#define dvd(x, n) vector<double> x(n); for (int i = 0; i < n; i++) cin >> x[i];
ll ipow(ll a,int b){ll r=1;for(;b;b>>=1,a*=a)if(b&1)r*=a;return r;}
template<class F>struct y_combinator{F f;template<class...Args>decltype(auto)operator()(Args&&...args)const{return f(*this,forward<Args>(args)...);}};
constexpr auto get_nums=[]<typename T>(T&&s){istringstream iss(forward<T>(s));return vector<int>{istream_iterator<int>{iss},{}};};
#define even(x) ((x)%2==0)
#define odd(x) ((x)%2!=0)
// clang-format on

int main() {
  fastio;
  dll(tall, wide);
  if (tall < 2 || wide < 2) {
    return 1;
    while (true) {
    }
  }
  if (odd(tall) && odd(wide)) {
    cout << "-1\n";
    return 0;
  }
  auto swapped = false;
  if (odd(tall)) {
    swap(tall, wide);
    swapped = true;
  }
  auto R = !swapped ? 'R' : 'D';
  auto L = !swapped ? 'L' : 'U';
  auto D = !swapped ? 'D' : 'R';
  auto U = !swapped ? 'U' : 'L';
  ll x = 1, y = 1;
  v<v<bool>> visited(wide, v<bool>(tall, false));

  ll c = 0;
  fr(i, 0, wide - 1) {
    cout << R;
    x++;
    c++;
    visited[x - 1][y - 1] = true;
  }
  fr(i, 0, tall - 1) {
    cout << D;
    y++;
    c++;
    visited[x - 1][y - 1] = true;
  }
  fr(i, 0, wide - 1) {
    cout << L;
    x--;
    c++;
    visited[x - 1][y - 1] = true;
  }
  cout << U;
  y--;
  c++;
  visited[x - 1][y - 1] = true;
  fr(i, 0, (tall - 2) / 2) {
    fr(j, 0, wide - 2) {
      cout << R;
      x++;
      c++;
      visited[x - 1][y - 1] = true;
    }
    cout << U;
    y--;
    c++;
    visited[x - 1][y - 1] = true;
    fr(j, 0, wide - 2) {
      cout << L;
      x--;
      c++;
      visited[x - 1][y - 1] = true;
    }
    cout << U;
    y--;
    c++;
    visited[x - 1][y - 1] = true;
  }
  dbg(c, wide * tall);
  dbg(x, y);
  if (c != wide * tall || x != 1 || y != 1) {
    while (true) {
    }
  }
  for (auto row : visited) {
    for (auto cell : row) {
      if (!cell) {
        while (true) {
        }
      }
    }
  }
  cout << '\n';
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED

Test 29

Verdict: ACCEPTED

Test 30

Verdict: ACCEPTED

Test 31

Verdict: ACCEPTED

Test 32

Verdict: ACCEPTED

Test 33

Verdict: ACCEPTED

Test 34

Verdict: ACCEPTED

Test 35

Verdict: ACCEPTED

Test 36

Verdict: ACCEPTED

Test 37

Verdict: ACCEPTED

Test 38

Verdict: ACCEPTED

Test 39

Verdict: ACCEPTED

Test 40

Verdict: ACCEPTED

Test 41

Verdict: ACCEPTED

Test 42

Verdict: ACCEPTED

Test 43

Verdict: ACCEPTED

Test 44

Verdict: ACCEPTED

Test 45

Verdict: ACCEPTED

Test 46

Verdict: ACCEPTED

Test 47

Verdict: ACCEPTED

Test 48

Verdict: ACCEPTED

Test 49

Verdict: ACCEPTED

Test 50

Verdict: ACCEPTED

Test 51

Verdict: ACCEPTED

Test 52

Verdict: ACCEPTED

Test 53

Verdict: ACCEPTED

Test 54

Verdict: ACCEPTED

Test 55

Verdict: ACCEPTED

Test 56

Verdict: ACCEPTED