#include <bits/stdc++.h>
#include <random>

#define MP make_pair


using namespace std;
using LL = long long;
using ULL = unsigned long long;

const int maxn = 1e5 + 5;



int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);

	int n, m, K;
	cin >> n >> m >> K;
	vector<string> str(n);
	vector<ULL> sd(n);

	vector<array<ULL, 4>> score(m);

	mt19937 rd(time(0));


	for(int i = 0; i < n; ++i){
		cin >> str[i];
		sd[i] = rd();
	}

	for(int j = 0; j < m; ++j){
		for(int c = 'A'; c <= 'D'; ++c){
			int bas = c - 'A';
			score[j][bas] = 0;
			for(int i = 0; i < n; ++i){
				if(str[i][j] != c){
					score[j][bas] += sd[i];
					// cerr << "not " << i << " " << (char(c)) << '\n';
				}
			}
			// cerr << "now " << j << " " << (char(c)) << " " << score[j][bas] << '\n';
 		}
	}
	
	ULL all = 0;
	for(int i = 0; i < n; ++i){
		all += sd[i] * K;
	}

	int ans = -1;
	for(int i = 0; i < n; ++i){
		ULL sum = 0;
		for(int j = 0; j < m; ++j){
			int bas = str[i][j] - 'A';
			sum += score[j][bas];
		}
		if(sum == all - K * sd[i]){
			ans = i;
		}
	}
	cout << ans + 1;
	return 0;
}