#include <bits/stdc++.h>
using namespace std;
string s[4101];
bitset<4100> bs[4101][4]; // a c g t
char luu[4] = {'A', 'C', 'G', 'T'};
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m, k;
cin >> n >> m >> k;
for (int i = 1;i<=n;++i){
cin >> s[i];
for (int j= 0;j<s[i].size();++j){
// cout << s[i][j] << '\n';
for (int p = 0;p<4;++p){
if(s[i][j]==luu[p]){
bs[i][p].set(j);
}
}
}
}
for (int i = 1;i<=n;++i){
bool c = true;
for (int j = 1;j<=n;++j){
if(i!=j){
int tmp = 0;
tmp += (bs[i][0] ^ bs[j][0]).count();
tmp += (bs[i][1] ^ bs[j][1]).count();
tmp += (bs[i][2] ^ bs[j][2]).count();
tmp += (bs[i][3] ^ bs[j][3]).count();
tmp/=2;
// cout << i << ' '<< j << ' ' << tmp << '\n';
if(tmp!=k){
c = false;
break;
}
}
}
if(c){
cout << i;
return 0;
}
}
}
