#include <bits/stdc++.h>
#define file_io freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
#define fast_io ios::sync_with_stdio(false);cin.tie(0);
#define what(x) cerr << #x << " is " << x << '\n';
#define kill(x) {cout << x << '\n'; return 0;}
#define all(x) (x).begin(), (x).end()
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pb push_back
#define ll long long
#define F first
#define S second
const ll inf = 1e18, mod = 1e9 + 7, delta = 1e9 + 9, SQ = 450, P = 6065621;
using namespace std;
const ll N = 110, LG = 20;
int dif[N][N];
string s[N];
int main() {
fast_io;
int n, m, k;
cin >> n >> m >> k;
for (int i = 1; i <= n; i++)
cin >> s[i];
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (i == j) continue;
int cnt = 0;
for (int x = 0; x < m; x++)
cnt += (s[i][x] != s[j][x]);
dif[i][j] = cnt;
}
}
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= n; j++) {
if (i == j) continue;
if (dif[i][j] != k) goto Hell;
}
kill(i);
Hell:;
}
return 0;
}
