//#include"holiday.h"
#include <bits/stdc++.h>
#define ll long long
#define rep(i,m,n) for(int i=(m); i<=(n); i++)
#define REB(i,m,n) for(int i=(m); i>=(n); i--)
#define pii pair<int,int>
#define pll pair<ll,ll>
#define MP make_pair
#define fs first
#define se second
#define bit(msk, i) ((msk >> i) & 1)
#define iter(id, v) for(auto id : v)
#define pb push_back
#define SZ(v) (ll)v.size()
#define ALL(v) v.begin(),v.end()
using namespace std;
mt19937_64 rd(chrono :: steady_clock :: now ().time_since_epoch().count());
ll Rand (ll l, ll r) { return uniform_int_distribution<ll> (l, r) (rd); }
const int N = 5e3 + 7;
const int Mod = 1e9 + 7;///lon
const ll INF = 1e18 + 7;
const ll BASE = 137;
const int szBL = 450;
vector<char> ch = {'A', 'C', 'G', 'T'};
int n, m, K;
string s[N];
int Col[N][255];
void solution() {
cin >> n >> m >> K;
rep (i, 1, n) {
cin >> s[i];
}
rep (j, 0, m - 1) {
rep (i, 1, n) Col[j][s[i][j]]++;
}
vector<int> cand;
rep (i, 1, n) {
int res = 0;
rep (j, 0, m - 1) {
iter (&c, ch) {
if (c != s[i][j]) res += Col[j][c];
}
}
if (res == K * (n - 1)) cand.pb(i);
}
random_shuffle(ALL(cand));
auto Distance = [&] (int i, int j) -> int {
int res = 0;
rep (k, 0, m - 1) {
if (s[i][k] != s[j][k]) ++res;
}
return res;
};
iter (&i, cand) {
bool ok = 1;
rep (j, 1, n) {
if (i != j && Distance(i, j) != K) {
ok = 0;
break;
}
}
if (ok) {
cout << i <<"\n";
return;
}
}
}
#define file(name) freopen(name".inp","r",stdin); \
freopen(name".out","w",stdout);
int main () {
// file("c");
ios_base :: sync_with_stdio(false); cin.tie(0); cout.tie(0);
int num_Test = 1;
// cin >> num_Test;
while (num_Test--)
solution();
}
/*
no bug challenge +36
10 2
1 2 3 1 4 5 1 2 1 2
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
1 10
4 9
*/
