#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
ll my_rand() { return (rand() * 100000ll + rand() * 100ll + (ll)rand()); }
const string dna = "ACGT";
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
int n, m, k;
cin >> n >> m >> k;
vector<vector<int> > v(n, vector<int>(m));
vector<vector<ll> > sum(m, vector<ll>(4, 0));
vector<ll> w(n);
ll ans = 0;
for (int i = 0; i < n; i++)
{
w[i] = my_rand();
string s; cin >> s;
for (int j = 0; j < m; j++)
{
v[i][j] = find(dna.begin(), dna.end(), s[j]) - dna.begin();
for (int c = 0; c < 4; c++) if (c ^ v[i][j]) sum[j][c] += w[i];
}
ans += w[i] * (ll)k;
}
for (int i = 0; i < n; i++)
{
ll my = w[i] * (ll)k;
for (int j = 0; j < m; j++) my += sum[j][v[i][j]];
if (my == ans)
{
cout << i+1 << "\n";
return 0;
}
}
return 0;
}
