#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
using namespace std;
#define ii pair<int , int>
#define iv pair<ii , ii>
#define iii pair<int , ii>
#define fi first
#define se second
#define int long long
const int inf = 1e18 + 7;
const int MAX_N = 4107;
const int MOD = 1e9 + 7;
bitset<4101> a[MAX_N];
bitset<4101> c;
int b[MAX_N][MAX_N];
signed main() {
ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
int n , m , k; cin >> n >> m >> k;
for (int i = 0 ; i < n ; i++) {
for (int j = 0 ; j < m ; j++) {
char x; cin >> x;
if (x == 'A') {
a[i][j] = 1;
}
else {
a[i][j] = 0;
}
}
}
for (int i = 0 ; i < n ; i++) {
for (int j = 0 ; j < i ; j++) {
c = a[i] ^ a[j];
int cnt = c.count();
if (cnt == k) b[i][j] = b[j][i] = 1;
else b[i][j] = b[j][i] = 0;
}
}
for (int i = 0 ; i < n ; i++) {
int cnt = 0;
for (int j = 0 ; j < n ; j++) {
cnt = cnt + (b[i][j] ? 1 : 0);
//cout << b[i][j] << " ";
}
if (cnt == (n - 1)) {
cout << i + 1;
return 0;
}
//cout << '\n';
}
return 0;
}
