#include <bits/stdc++.h>
#define ll long long
#define lsb(x) (x & -x)
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
//freopen("a.in", "r", stdin);
//freopen("a.out", "w", stdout);
int n, m, k;
cin >> n >> m >> k;
k = m - k;
vector<int> code(30, 0);
code['A' - 'A'] = 1;
code['C' - 'A'] = 2;
code['G' - 'A'] = 3;
code['T' - 'A'] = 4;
vector<vector<vector<ll>>> v(5, vector<vector<ll>> (n + 1, vector<ll> (m + 1, 0)));
for(int i = 1; i <= n; i ++) {
string s;
cin >> s;
for(int j = 0; j < m; j ++)
v[code[s[j] - 'A']][i][j + 1] = 1;
}
srand(time(NULL));
vector<ll> hs(n + 1, 0);
for(int i = 1; i <= n; i ++)
hs[i] = rand();
vector<ll> ans(n + 1, 0);
vector<ll> ths(m + 1, 0);
for(int color = 1; color <= 4; color ++) {
for(int i = 1; i <= m; i ++)
ths[i] = 0;
for(int i = 1; i <= m; i ++)
for(int k = 1; k <= n; k ++)
ths[i] += (v[color][k][i] * hs[k]);
for(int i = 1; i <= n; i ++)
for(int k = 1; k <= m; k ++)
ans[i] += (v[color][i][k] * ths[k]);
}
vector<ll> solhs(n + 1, 0);
for(int i = 1; i <= n; i ++) {
for(int j = 1; j <= n; j ++) {
if(i == j)
solhs[i] += (m * hs[j]);
else
solhs[i] += (k * hs[j]);
}
}
for(int i = 1; i <= n; i ++) {
if(solhs[i] == ans[i]) {
cout << i;
return 0;
}
}
return 0;
}
