#include <bits/stdc++.h>
#define int long long
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
using namespace std;
int popcount_u128(__uint128_t value) {
// Cast and split into two 64-bit halves
uint64_t lower = (uint64_t)value; // Lower 64 bits
uint64_t upper = (uint64_t)(value >> 64); // Upper 64 bits
// Use __builtin_popcountll for each half and sum the results
return __builtin_popcountll(lower) + __builtin_popcountll(upper);
}
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr);
int n,m,k; cin >> n >> m >> k;
int blocks=(m/128)+1;
vector<vector<__uint128_t>> a_c(n,vector<__uint128_t>(blocks+1));
vector<vector<__uint128_t>> g_t(n,vector<__uint128_t>(blocks+1));
vector<int> c(n);
int mn=1e18;
int mx=0;
for (int i = 0; i < n; i++)
{
int j=0;
int bl=0;
while(j<m){
char hc; cin >> hc;
if(hc=='A') {
a_c[i][bl]+=((__uint128_t)1<<j);
c[i]++;
}
j++;
if(j%128==0) bl++;
}
mn=min(mn,c[i]);
mx=max(mx,c[i]);
}
vector<vector<int>> dist(n,vector<int>(n,1e18));
for (int i = 0; i < n; i++)
{
if(c[i]-mn>k||mx-c[i]>k) continue;
for (int j = 0; j < n; j++)
{
if(i==j) continue;
if(dist[i][j]<1e18) continue;
dist[i][j]=0;
for (int _k = 0; _k < blocks; _k++)
{
dist[i][j]+=popcount_u128(a_c[i][_k]^a_c[j][_k]);
}
dist[j][i]=dist[i][j];
}
}
for (int i = 0; i < n; i++)
{
if(c[i]-mn>k||mx-c[i]>k) continue;
bool b=true;
for (int j = 0; j < n; j++)
{
if(i==j) continue;
if(dist[i][j]!=k) { b=false; break; }
}
if(b==true){
cout << i+1 << "\n";
break;
}
}
return 0;
}
