// Hydro submission #66f2aa029b5bc2742032790c@1727179266719
#include <bits/stdc++.h>

using ULL = unsigned long long;

std::mt19937_64 rng((std::random_device())());

constexpr int N = 100005;

int n, m, k;
std::string s[N];
ULL val[N], sum[N][4];

int main() {
    std::cin >> n >> m >> k;
    ULL need = 0;
    for (int i = 0; i < n; i++) {
        val[i] = rng();
        need += val[i] * (m - k);
        std::cin >> s[i];
        for (int j = 0; j < m; j++) sum[j][s[i][j] - 'A'] += val[i];
    }
    int ans = -1;
    for (int i = 0; i < n; i++) {
        ULL cur = 0;
        for (int j = 0; j < m; j++) cur += sum[j][s[i][j] - 'A'];
        if (cur == need + k * val[i]) ans = i;
    }
    printf("%d\n", ans + 1);
    return 0;
}