#include <bits/stdc++.h>
using namespace std; 
const int N = 4105; 

int n, m, k; 
struct Node {
    char a[N];
    int id;
} a[N];
bitset<N> b[N][4]; 
inline int get(char ch) {
    if (ch == 'A') return 0; 
    if (ch == 'T') return 1; 
    if (ch == 'G') return 2; 
    return 3; 
}

mt19937 Rand(time(0)); 

int main(void) {
    ios::sync_with_stdio(0); cin.tie(0); 
    cin >> n >> m >> k; 
    for (int i = 1; i <= n; ++i) cin >> a[i].a + 1, a[i].id = i; 
    shuffle(a + 1, a + n + 1, Rand); 
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            b[i][get(a[i].a[j])][j] = 1; 
    for (int i = 1; i <= n; ++i) {
        bool flag = 0; 
        for (int j = 1; j <= n; ++j) if (i != j) {
            int s = 0;
            for (int p = 0; p < 4; ++p) s += (b[i][p] & b[j][p]).count();
            if (s + k != m) { flag = 1; break; }
        }
        if (!flag) return cout << a[i].id << '\n', 0; 
    }
    return 0;
}