Skittles

#include <iostream>

using namespace std;

const int N = 1e5 + 5;
const int MOD = 998244353;

void add(int &a, int b) {
  a += b;
  if (a >= MOD) {
    a -= MOD;
  }
}

int mul(int a, int b) {
  return 1LL * a * b % MOD;
}

int mod_pow(int a, int b) {
  int r = 1;
  for (; b > 0; a = mul(a, a), b >>= 1) {
    if (b & 1) {
      r = mul(r, a);
    }
  }
  return r;
}

int mod_inv(int a) {
  return mod_pow(a, MOD - 2);
}

int n;
int a, b;
int f[2 * N], inv[2 * N];

int C(int n, int k) {
  if (k > n || n < 0 || k < 0) {
    return 0;
  }
  int r = f[n];
  r = mul(r, inv[k]);
  r = mul(r, inv[n - k]);
  return r;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  f[0] = 1;
  for (int i = 1; i < 2 * N; i++) {
    f[i] = mul(i, f[i - 1]);
  }
  inv[2 * N - 1] = mod_inv(f[2 * N - 1]);
  for (int i = 2 * N - 2; i >= 0; i--) {
    inv[i] = mul(i + 1, inv[i + 1]);
  }
  cin >> n >> a >> b;
  int ans = 0;
  for (int c = a; c <= b; c++) {
    add(ans, C(c + n - 1, c));
  }
  cout << ans << '\n';
  return 0;
}

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

Test 57

Verdict: ACCEPTED

Test 58

Verdict: ACCEPTED

Test 59

Verdict: ACCEPTED

Test 60

Verdict: ACCEPTED

Test 61

Verdict: ACCEPTED

Test 62

Verdict: ACCEPTED

Test 63

Verdict: ACCEPTED