#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pll pair<long long, long long>
#define pb push_back
#define F first
#define S second
#define all(x) (x).begin(), (x).end()
const ll N = 4200;
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ll block = 350;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll get_rand(ll l, ll r) {
assert(l <= r);
return uniform_int_distribution<ll> (l, r)(rng);
}
ll n,m,k;
ll r[N], cnt[N], res[N];
char a[N][N];
void to_thic_cau(){
cin >> n >> m >> k;
for(int i = 1; i <= n;i++){
for(int j = 1; j <= m;j++) cin >> a[i][j];
}
for(int i = 1; i <= n;i++) r[i] = get_rand(1,(ll)1e12);
for(int j = 1; j <= m;j++){
cnt['A'] = cnt['T'] = cnt['G'] = cnt['C'] = 0;
ll tot = 0;
for(int i = 1; i <= n;i++){
cnt[int(a[i][j])] += r[i];
tot += r[i];
}
for(int i = 1; i <= n;i++) res[i] += tot - cnt[int(a[i][j])];
}
ll tot = 0;
for(int i = 1; i <= n;i++) tot += r[i];
for(int i = 1; i <= n;i++){
if(res[i] == (tot - r[i]) * k){
cout << i << '\n';
return;
}
}
}
signed main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
ll tc = 1;
//cin >> tc;
while(tc--) to_thic_cau();
}
