#include <bits/stdc++.h>
using namespace std;
#define rep(i, a, b) for(int i = (a); i < int(b); ++i)
#define rrep(i, a, b) for(int i = (a) - 1; i >= int(b); --i)
#define trav(it, v) for(auto &it : (v))
#define all(v) (v).begin(), (v).end()
#define what_is(x) cerr << #x << " is " << x << endl;
#define sz(x) (int)(x).size()
typedef double fl;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pii> vpi;
int main(){
ios::sync_with_stdio(0);
int N, M, K;
cin >> N >> M >> K;
vector<string> dna = vector<string>(N);
set<int> candidates;
rep(i,0,N) {
candidates.insert(i);
cin >> dna[i];
}
while (candidates.size() > 1) {
vector<int> check;
vector<bool> isChecked(N);
rep(i,0,N) {
if (rand()%2) {
check.push_back(i);
isChecked[i] = true;
}
}
vector<int> tot[128];
tot['A'].resize(M);
tot['C'].resize(M);
tot['G'].resize(M);
tot['T'].resize(M);
for (int i : check) {
rep(j,0,M) {
tot[(int)dna[i][j]][j]++;
}
}
set<int> newCandidates;
for (int i : candidates) {
int correct = 0;
rep(j,0,M) {
correct += tot[(int)dna[i][j]][j];
}
if (correct - M*isChecked[i] == (M-K) * ((int)check.size() - isChecked[i])) {
newCandidates.insert(i);
}
}
candidates = newCandidates;
}
cout << (*candidates.begin()) + 1 << endl;
}
