#include <bits/stdc++.h>
using namespace std;
int n, m, k;
int main() {
cin.sync_with_stdio(false);
cin >> n >> m >> k;
vector<bitset<4100>> alines(n), glines(n), tlines(n), clines(n);
for (int i = 0; i < n; i++) {
string line;
cin >> line;
for (int j = 0; j < m; j++) {
if (line[j] == 'A')
alines[i][j] = 1;
if (line[j] == 'C')
glines[i][j] = 1;
if (line[j] == 'T')
tlines[i][j] = 1;
if (line[j] == 'G')
clines[i][j] = 1;
}
}
random_device rd;
mt19937 g(rd());
vector<int> order(n);
for (int i = 0; i < n; i++)
order[i] = i;
shuffle(order.begin(), order.end(), g);
bitset<4100> is_good = bitset<4100>();
for (int i = 0; i < n; i++)
is_good[i] = 1;
for (int i = 0; i < n; i++) {
for (int j = i + 1; j < n; j++) {
int diff = (alines[order[i]] ^ alines[order[j]]).count() +
(glines[order[i]] ^ glines[order[j]]).count() +
(tlines[order[i]] ^ tlines[order[j]]).count() +
(clines[order[i]] ^ clines[order[j]]).count();
if (diff / 2 != k) {
is_good[order[i]] = 0;
is_good[order[j]] = 0;
}
}
}
assert(is_good.count() == 1);
cout << is_good._Find_first() + 1 << endl;
}
