#include <bits/stdc++.h>

using namespace std;

using LL = long long;
using ULL = unsigned long long;

mt19937_64 gen;

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

    int n, m, k;
    m = 10;
    cin >> n >> m >> k;
    k = m - k;
    vector<string> a(n);
    for (auto &s : a)
    {
        cin >> s;
    }
    vector<ULL> val(n);
    generate(val.begin(), val.end(), gen);
    ULL vs = 0;
    for (auto v : val)
    {
        vs += v;
    }
    vector<array<ULL, 4>> sum(m);
    for (int i = 0; i < n; ++i)
    {
        for (int j = 0; j < m; ++j)
        {
            sum[j][a[i][j] - 'A'] += val[i];
        }
    }
    for (int i = 0; i < n; ++i)
    {
        ULL cs = 0;
        for (int j = 0; j < m; ++j)
        {
            cs += sum[j][a[i][j] - 'A'];
        }
        if (cs == vs * k + val[i] * (m - k))
        {
            cout << i + 1 << '\n';
            return 0;
        }
    }
}