#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define fastio ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
using namespace std;
using namespace __gnu_pbds;
typedef tree<ll, null_type, less<ll>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
ordered_set st;
ll N,M,K;
string s[5005];
bool b[5005];
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
int main(){
cin>>N>>M>>K;
for(int i=0;i<N;i++){
cin>>s[i];
st.insert(i);
}
while(st.size()>2){
ll x=rng()%st.size();
ll y=rng()%st.size();
if(x==y){
continue;
}
ll cnt=0;
for(int j=0;j<M;j++){
if(s[x][j]!=s[y][j]){
cnt++;
}
}
if(cnt!=K){
st.erase(x);
st.erase(y);
}
}
if(st.size()==1){
cout<<*st.find_by_order(0)+1<<endl;
}
else{
ll x=*st.find_by_order(0);
bool ok=true;
for(int i=0;i<N;i++){
if(i==x){
continue;
}
ll cnt=0;
for(int j=0;j<M;j++){
if(s[i][j]!=s[x][j]){
cnt++;
}
}
if(cnt!=K){
ok=false;
break;
}
}
if(ok){
cout<<x+1<<endl;
}
else{
cout<<*st.find_by_order(1)+1<<endl;
}
}
}
