Distinct sums

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

#ifdef LOCAL
#define D(x) {x;}
#else
#define D(x)
#endif
#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()
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;

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

    int n;
    cin >> n;

    if (n % 2 == 1) {
        cout << "IMPOSSIBLE" << endl;
        return 0;
    }

    for (int i = 1; i <= n; ++i) {
        int k = n-i;
        for (int j = 1; j <= k; ++j) cout << 2;
        if (i > n/2) cout << 1;
        else cout << 2;
        for (int j = k+2; j <= n; ++j) cout << 0;
        cout << endl;
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: ACCEPTED

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: ACCEPTED

Test 9

Verdict: WRONG ANSWER

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: ACCEPTED

Test 12

Verdict: WRONG ANSWER

Test 13

Verdict: ACCEPTED