Distinct sums

#include <bits/stdc++.h>
typedef long long ll;
typedef long double ld;
using namespace std;
#define F first
#define S second
#define X real()
#define Y imag()

int ans[1010][1010];

int main() {
    int n;
    cin>>n;
    if (n%2) {
        cout<<"IMPOSSIBLE\n";
    } else {
        cout<<"YES\n";
        for (int a=0;2*a<n;a++) {
            for (int i=a;i+a<n;i++) ans[a][i]=0;
            for (int j=a;j+a<n;j++) ans[j][a]=0;
            ans[n-a-1][a]=1;
            for (int i=a+1;i+a<n;i++) ans[n-a-1][i]=2;
            for (int j=a+1;j+a<n;j++) ans[j][n-a-1]=2;
        }
        for (int i=0;i<n;i++) {
            for (int j=0;j<n;j++) {
                cout<<ans[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