#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,popcnt")
#define ll long long
#define pll pair<ll,ll>
#define pii pair<int,int>
#define fs first
#define sc second
#define tlll tuple<ll,ll,ll>
const int mxn = 4140;
int arr[mxn][mxn];
int N,M,K;
vector<int> v,cand;
const int magic = 20;
bitset<mxn> in;
const int lim = 1.95*CLOCKS_PER_SEC;
int st;
int dif(int a,int b){
int re = 0;
for(int i = 0;i<M;i++){
re += (arr[a][i] != arr[b][i]);
}
return re;
}
void collect(){
for(int i = 0;i<N;i++){
for(int j = i+1;j<N;j++){
if(dif(i,j) != K){
if(!in[i])v.push_back(i);
if(!in[j])v.push_back(j);
if(v.size()>=magic)return;
in[i] = in[j] = true;
}
}
if(!in[i]){
cout<<i+1;
exit(0);
}
}
return;
}
int main(){
st = clock();
ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>N>>M>>K;
for(int i = 0;i<N;i++){
for(int j = 0;j<M;j++){
char c;
cin>>c;
arr[i][j] = c-'A';
}
}
collect();
for(int i = 0;i<N;i++){
if(in[i])continue;
bool flag = true;
for(auto &j:v){
if(dif(i,j) != K)flag = false;
}
if(flag)cand.push_back(i);
}
assert(cand.size()<100);
for(auto &i:cand){
bool flag = true;
for(int j = 0;j<N;j++){
if(i == j)continue;
if(dif(i,j) != K){
flag = false;
break;
}
}
if(flag){
cout<<i+1;
return 0;
}
}
assert(false);
}
