This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
//#pragma GCC optimize("Ofast,O3,unroll-loops")
//#pragma GCC target("avx2")
#include <bits/stdc++.h>
using namespace std;
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define bpc(x) __builtin_popcount(x)
#define bpcll(x) __builtin_popcountll(x)
#define MP make_pair
//#define endl '\n'
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
typedef long long ll;
const int MOD = 1e9 + 7;
const int N = 4101;
int cnt[N][N];
string s[N];
bitset<N> b[N];
void solve(){
    int n, m, k;
    cin >> n >> m >> k;
    for (int i = 0; i < n; i++) cin >> s[i];
    if (max(n, m) <= 1800) {
        for (char c: "ACGT") {
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < m; j++) {
                    if (s[i][j] == c) {
                        b[i].set(j);
                    } else {
                        b[i].reset(j);
                    }
                }
            }
            for (int i = 0; i < n; i++) {
                for (int j = 0; j < i; j++) {
                    int x = (b[i] & b[j]).count();
                    cnt[i][j] += x;
                    cnt[j][i] += x;
                }
            }
        }
    } else {
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                if (s[i][j] == 'A') {
                    b[i].set(j);
                } else {
                    b[i].reset(j);
                }
            }
        }
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < i; j++) {
                int x = (b[i] ^ b[j]).count();
                x = m - x;
                cnt[i][j] += x;
                cnt[j][i] += x;
            }
        }
    }
    for (int i = 0; i < n; i++){
        bool ok = true;
        for (int j = 0; j < n; j++){
            if (i != j && cnt[i][j] != m - k) ok = false;
        }
        if (ok){
            cout << i + 1 << endl;
            return;
        }
    }
}
int main(){
    clock_t startTime = clock();
    ios_base::sync_with_stdio(false);
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int test_cases = 1;
//    cin >> test_cases;
    for (int test = 1; test <= test_cases; test++){
        // cout << (solve() ? "YES" : "NO") << endl;
        solve();
    }
#ifdef LOCAL
    cerr << "Time: " << int((double) (clock() - startTime) / CLOCKS_PER_SEC * 1000) << " ms" << endl;
#endif
    return 0;
}
Compilation message (stderr)
genetics.cpp: In function 'int main()':
genetics.cpp:88:13: warning: unused variable 'startTime' [-Wunused-variable]
   88 |     clock_t startTime = clock();
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