#include <bits/stdc++.h>
using namespace std;

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	mt19937_64 rnd(chrono::system_clock::now().time_since_epoch().count());
	int n, m, k;
	cin >> n >> m >> k;
	vector<string> s(n);
	vector<unsigned long long> h(n);
	vector<vector<unsigned long long>> sum(m, vector<unsigned long long>(4));
	unsigned long long total = 0;
	for (int i = 0; i < n; ++i) {
		h[i] = rnd();
		cin >> s[i];
		for (int j = 0; j < m; ++j) {
			sum[j][(int) (s[i][j] - 'A')] += h[i];
		}
		total += h[i] * (m - k);
	}    
	for (int i = 0; i < n; ++i) {
		unsigned long long required = total - h[i] * (m - k);
		unsigned long long cur = 0;
		for (int j = 0; j < m; ++j) {
			cur += sum[j][(int) (s[i][j] - 'A')] - h[i];
		}
		if (cur == required) {
			cout << i + 1 << '\n';
			return 0;
		}
	}
	return 0;
}