#include <bits/stdc++.h>
using namespace std;
map<char, int> mp;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
mp['A'] = 0, mp['C'] = 1, mp['G'] = 2, mp['T'] = 3;
int n, m, k;
cin >> n >> m >> k;
vector<string> a(n);
vector<long long> w(n);
iota(w.begin(), w.end(), 1);
random_shuffle(w.begin(), w.end());
for (int i = 0; i < n; i++) {
cin >> a[i];
}
vector< vector<long long> > v(4, vector<long long>(m, 0));
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
v[mp[a[i][j]]][j] += w[i];
}
}
for (int i = 0; i < n; i++) {
long long tmp = 0;
for (int j = 0; j < m; j++) {
tmp += v[mp[a[i][j]]][j];
}
long long exp = 0;
for (int j = 0; j < n; j++) {
if (j != i) {
exp += w[j];
}
}
exp *= (long long) (m - k);
exp += (long long) m * w[i];
if (tmp == exp) {
cout << i + 1 << '\n';
return 0;
}
}
return 0;
}
