/*
* Author: Nonoze
* Created: Thursday 06/03/2025
*/
#include <bits/stdc++.h>
using namespace std;
#ifndef IN_LOCAL
#define dbg(...)
#endif
// #define cout cerr << "OUT: "
#define endl '\n'
#define endlfl '\n' << flush
#define quit(x) return (void)(cout << x << endl)
template<typename T> void read(T& x) { cin >> x;}
template<typename T1, typename T2> void read(pair<T1, T2>& p) { read(p.first), read(p.second);}
template<typename T> void read(vector<T>& v) { for (auto& x : v) read(x); }
template<typename T1, typename T2> void read(T1& x, T2& y) { read(x), read(y); }
template<typename T1, typename T2, typename T3> void read(T1& x, T2& y, T3& z) { read(x), read(y), read(z); }
template<typename T1, typename T2, typename T3, typename T4> void read(T1& x, T2& y, T3& z, T4& zz) { read(x), read(y), read(z), read(zz); }
template<typename T> void print(vector<T>& v) { for (auto& x : v) cout << x << ' '; cout << endl; }
#define sz(x) (int)(x.size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define make_unique(v) sort(all(v)), v.erase(unique(all(v)), (v).end())
#define pb push_back
#define mp(a, b) make_pair(a, b)
#define fi first
#define se second
#define cmin(a, b) a = min(a, b)
#define cmax(a, b) a = max(a, b)
#define YES cout << "YES" << endl
#define NO cout << "NO" << endl
#define QYES quit("YES")
#define QNO quit("NO")
#define int long long
#define double long double
const int inf = numeric_limits<int>::max() / 4;
mt19937 rng(123);
const int MOD = 1e9+7, LOG=20;
void solve();
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
int tt=1;
// cin >> tt;
while(tt--) solve();
return 0;
}
int n, k, m, q;
vector<vector<int>> a;
void solve() {
read(n, m, k);
a.clear(), a.resize(n);
for (int i=0; i<n; i++) {
string s; read(s);
for (int j=0; j<m; j++) {
if (s[j]=='A') a[i].pb(0);
else if (s[j]=='C') a[i].pb(1);
else if (s[j]=='T') a[i].pb(2);
else a[i].pb(3);
}
}
vector<vector<int>> freq(m, vector<int>(4));
vector<int> weight;
int sm=0;
for (int i=0; i<n; i++) {
int nb=rng()%(int)(1e10);
sm+=nb, weight.pb(nb);
for (int j=0; j<m; j++) freq[j][a[i][j]]+=nb;
}
for (int i=0; i<n; i++) {
int val=0;
for (int j=0; j<m; j++) val+=sm-freq[j][a[i][j]];
if (val==(sm-weight[i])*k) quit(i+1);
}
}
