#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#pragma GCC optimize("unroll-loops,no-stack-protector")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;
typedef long double ld;
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
ll n,m,k;
cin >> n >> m >> k;
vector <string> arr(n);
bitset<1801> s[n];
for (int z=0;z<n;z++){
cin >> arr[z];
for (int x=0;x<m;x++){
if (arr[z][x] == 'A') s[z][x] = 1;
else s[z][x] = 0;
}
}
if (n <= 100){
for (int z=0;z<n;z++){
bool ok = true;
for (int x=0;x<n;x++){
if (z == x) continue;
ll c = 0;
for (int q=0;q<m;q++){
if (arr[z][q] != arr[x][q]) c++;
}
if (c != k){
ok = false;
break;
}
}
if (ok){
cout << z+1 << endl;
return 0;
}
}
} else {
for (int z=0;z<n;z++){
bool ok = true;
for (int x=0;x<n;x++){
if (z == x) continue;
bitset <1801> temp;
temp = s[z]^s[x];
ll c = temp.count();
if (c != k){
ok = false;
break;
}
}
if (ok){
cout << z+1 << endl;
return 0;
}
}
}
}
