#include <bits/stdc++.h>

#define lsb(x) (x & (-x))

using ull = unsigned long long;
using ll = long long;

using namespace std;



int main() {
#ifdef HOME
    ifstream cin("input.in");
    ofstream cout("output.out");
#endif
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int n, m, k;
    cin >> n >> m >> k;

    vector<string> str(n);
    for (auto& s : str) {
        cin >> s;
    }

    vector<vector<int>> freq(m, vector<int>(4));
    for (auto& s : str) {
        for (int i = 0; i < m; i++) {
            freq[i][s[i] - 'A']++;
        }
    }

    vector<int> order(n);
    iota(order.begin(), order.end(), 0);
    sort(order.begin(), order.end(), [&](const int& a, const int& b) {
        return str[a] < str[b];
    });

    for (int i = 0; i < n; i++) {
        if (i != 0 && str[order[i]] == str[order[i - 1]]) continue;

        int total = 0;
        for (int j = 0; j < m; j++) {
            total += n - freq[j][str[order[i]][j] - 'A'];
        }

        if (total != (n - 1) * k) {
            continue;
        }

        bool bad = false;
        for (int i1 = 0; i1 < n; i1++) {
            if (i == i1) continue;

            int curr = 0;
            for (int j = 0; j < m; j++) {
                curr += (str[order[i]][j] != str[order[i1]][j]);
            }
            // cerr << i << " " << curr << "\n";
            if (curr != k) {
                bad = true;
            }
        }

        if (!bad) {
            cout << order[i] + 1 << "\n";
            return 0;
        }
    }

    return 0;
}