#include <bits/stdc++.h>
using namespace std;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
const int N = 4005;
string s[N];
int n, m, k;
int calc(int i, int j) {
int res = 0;
for (int x = 0; x < m; x++)
res += s[i][x] != s[j][x];
return res;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
cin >> n >> m >> k;
vector<int> can;
for (int i = 0; i < n; i++) {
cin >> s[i];
if (can.empty())
can.push_back(i);
else if (calc(can.back(), i) != k)
can.pop_back();
else can.push_back(i);
}
for (int i : can) {
vector<int> ord(n);
iota(ord.begin(), ord.end(), 0);
shuffle(ord.begin(), ord.end(), rng);
bool flag = true;
for (int j : ord)
if (i != j && calc(i, j) != k) {
flag = false; break;
}
if (flag) return cout << i + 1, 0;
}
}
