Distinct sums

#include <bits/stdc++.h>
using namespace std;

#define rep(i, a, b) for(int i = a; i < (b); i++)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int N = 1005;

int a[N][N];

int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin.exceptions(cin.failbit);

    int n;
    cin >> n;


    if (n & 1) {
        cout << "IMPOSSIBLE";
        return 0;
    }

    int sz = 2;
    for (int i = 1; i < n; i += 2) {
        a[i][n - sz] = 1;
        a[i][n - sz + 1] = 2;
        for (int j = n - sz + 1 + 1; j < n; j++) a[i][j] = 2;
        for (int j = n - sz; j < n; j++) a[i + 1][j] = 2;
        sz += 2;
    }

    cout << "YES\n";
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cout << a[i][j] << ' ';
        }
        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