#include <bits/stdc++.h>
using namespace std;
#define int long long
int getIndex(char c){
if(c == 'A') return 0;
if(c == 'C') return 1;
if(c == 'G') return 2;
return 3;
}
vector< vector< vector< int > > > opti(4, vector< vector< int > > (65, vector< int >(4500)));
int compare(int a, int b){
int tot = 0;
for(int i = 0; i < 65; i++){
for(int j = 0; j < 4; j++){
tot += __builtin_popcountll(opti[j][i][a] ^ opti[j][i][b]);
}
}
return tot/2;
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, K;
cin >> n >> m >> K;
vector< string > v(n);
for(int i = 0; i < n; i++){
cin >> v[i];
vector< vector< int > > nb(4, vector< int >(65));
for(int j = 1; j <= 65; j++){
for(int k = (j-1)*64; k < min(j*64, m); k++){
nb[getIndex(v[i][k])][j-1] ^= (1LL<<(63-k%64));
}
}
for(int k = 0; k < 4; k++){
for(int l = 0; l < 65; l++){
opti[k][l][i] = nb[k][l];
}
}
}
/*
for(int i = 0; i < n; i++){
cout << "NUMBER " << i << endl;
for(int j = 0; j < 4; j++){
cout << opti[j][0][i] << endl;
}
}*/
for(int i = 0; i < n; i++){
bool verif = true;
for(int j = 0; j < n; j++){
if(j == i) continue;
if(compare(i,j) != K){
verif = false;
break;
}
}
if(verif){
cout << i+1 << endl;
return 0;
}
}
}
