#include <bits/stdc++.h>
#define ZAZO ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")
using namespace std;
// i have maximum 65 chuncks , each chuck will have 64 bits (elements)
unsigned long long bits[4100][65],bits2[4100][65];
int n , m , k ;
bool check(int x , int y)
{
int cnt=0;
for(int i = 0 ; i < 65 ; i++)
cnt += __builtin_popcountll((bits[x][i]^bits[y][i])|(bits2[x][i]^bits2[y][i]));
if(cnt == k) return true;
return false;
}
int32_t main() {
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ZAZO
cin >> n >> m >> k;
int for_hamatcha[n];
for(int i = 0 ; i < n ; i++)
{
for_hamatcha[i]=i;
for(int j = 0 ; j < m ; j ++)
{
char s; cin >> s;
// get the bit you want by checking mod
unsigned long long pos = ((unsigned long long) 1<<j%64);
// set the bit to one in the specific place in the specific chunk;
if(s == 'C') bits[i][j/64] |= pos;
else if(s == 'T') bits[i][j/64] |= pos , bits2[i][j/64] |= pos;
else if(s == 'G') bits2[i][j/64] |= pos;
}
}
shuffle(for_hamatcha,for_hamatcha+n,rng);
int ans[n]={0};
for(int i = 0 ; i < n ; i ++)
{
if(ans[for_hamatcha[i]]==-1) continue;
int flg=0;
for(int j = 0 ; j < n ; j ++)
{
if(for_hamatcha[i]==for_hamatcha[j]) continue;
bool ok = check(for_hamatcha[i] , for_hamatcha[j]);
if(!ok)
{
flg=1;
ans[for_hamatcha[i]]=-1;
ans[for_hamatcha[j]]=-1;
break;
}
}
if(!flg){
cout<<for_hamatcha[i]+1;
return 0;
}
}
}
