Distinct sums

#include <bits/stdc++.h>

using namespace std;

using ll = long long;

const int MAX_N = 1e3 + 23;

int main()
{
    ios_base::sync_with_stdio(false);

    int n;
    cin >> n;

    if (n % 2 != 0)
    {
        cout << "IMPOSSIBLE\n";
        return 0;
    }

    cout << "YES\n";

    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            // check diagonal
            if (i == (n - 1 - j))
            {
                if (i < (n / 2))
                    cout << 0 << ' ';
                else
                    cout << 1 << ' ';
            }
            else if (i < (n - 1 - j))
            {
                cout << 0 << ' ';
            }
            else
            {
                cout << 2 << ' ';
            }
        }
        cout << '\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