#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main() {
    int N, K;
    cin >> N >> K;
    vector<string> S(N);
    for (int i = 0; i < N; i++) {
        cin >> S[i];
    }
    
    vector<vector<int>> dist(N, vector<int>(N, 0));
    for (int i = 0; i < N; i++) {
        for (int j = i + 1; j < N; j++) {
            for (int k = 0; k < K; k++) {
                if (S[i][k] != S[j][k]) {
                    dist[i][j]++;
                }
            }
            dist[j][i] = dist[i][j];
        }
    }
    
    vector<double> avgdist(N, 0.0);
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            if (i != j) {
                avgdist[i] += dist[i][j];
            }
        }
        avgdist[i] /= (N - 1);
    }
    
    int min_index = min_element(avgdist.begin(), avgdist.end()) - avgdist.begin();
    cout << min_index << endl;
    
    return 0;
}