#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>
// #include <ext/rope>
using namespace std;
// using namespace __gnu_cxx;
// using namespace __gnu_pbds;
void Hollwo_Pelw();
signed main(){
#ifndef hollwo_pelw_local
if (fopen(".inp", "r"))
assert(freopen(".inp", "r", stdin)), assert(freopen(".out", "w", stdout));
#else
using namespace chrono;
auto start = steady_clock::now();
#endif
cin.tie(0), cout.tie(0) -> sync_with_stdio(0);
int testcases = 1;
// cin >> testcases;
for (int test = 1; test <= testcases; test++){
// cout << "Case #" << test << ": ";
Hollwo_Pelw();
}
#ifdef hollwo_pelw_local
auto end = steady_clock::now();
cout << "\nExecution time : " << duration_cast<milliseconds> (end - start).count() << "[ms]" << endl;
#endif
}
const int N = 4100;
const string G = "ACGT";
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int n, m, k, p[N];
string s[N];
bitset<N> f[N][4];
inline int diff(int i, int j) {
int res = 0;
for (int x = 0; x < 4; x++)
res += (f[i][x] ^ f[j][x]).count();
return res / 2;
}
void Hollwo_Pelw(){
cin >> n >> m >> k;
for (int i = 0; i < n; i++) {
cin >> s[i];
for (int j = 0; j < m; j++)
for (int x = 0; x < 4; x++)
if (G[x] == s[i][j]) f[i][x].set(j);
}
iota(p, p + n, 0);
shuffle(p, p + n, rng);
for (int i = 0; i < n; i++) {
bool ok = 1;
for (int j = 0; j < n && ok; j++) {
if (i == j) continue;
if (diff(p[i], p[j]) != k) ok = 0;
}
if (ok) {
cout << p[i] + 1 << '\n';
return ;
}
}
}
