#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define fi first
#define se second
int n,m,k;
vector<ull>ab[100001],ac[100001],ad[100001];
int p[100001];

int main(){
	ios::sync_with_stdio(false);cin.tie(0);
	cin >> n >> m >> k;
	int bc=(m-1)/64+1;
	for(int i=1; i<=n ;i++){
		string s;cin >> s;
		ab[i].resize(bc);
		ac[i].resize(bc);
		ad[i].resize(bc);
		for(int j=0; j<m ;j++){
			ab[i][j/64]|=(s[j]=='A' || s[j]=='B')*(1ull<<(j%64));
			ac[i][j/64]|=(s[j]=='A' || s[j]=='C')*(1ull<<(j%64));
			ad[i][j/64]|=(s[j]=='A' || s[j]=='D')*(1ull<<(j%64));
		}
		p[i]=i;
	}
	random_shuffle(p+1,p+n+1);
	for(int i=1; i<=n ;i++){
		bool fail=false;
		for(int j=1; j<=n ;j++){
			if(i==p[j]) continue;
			int x=0;
			for(int k=0; k<bc ;k++){
				x+=__builtin_popcountll(ab[i][k]^ab[p[j]][k]);
				x+=__builtin_popcountll(ac[i][k]^ac[p[j]][k]);
				x+=__builtin_popcountll(ad[i][k]^ad[p[j]][k]);
			}
			x/=2;
			//cout << i << ' ' << p[j] << ' ' << x << endl;
			if(x!=k){
				fail=true;
				break;
			}
		}
		if(!fail) return cout << i << '\n',0;
	}
}