#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
#define ar array
#define pb push_back
#define ln '\n'
#define size(x) (int)(x).size()
#define int long long
typedef pair <int,int> pii;
using i64 = long long;
template <class F, class _S>
bool chmin(F &u, const _S &v){
bool flag = false;
if ( u > v ){
u = v; flag |= true;
}
return flag;
}
template <class F, class _S>
bool chmax(F &u, const _S &v){
bool flag = false;
if ( u < v ){
u = v; flag |= true;
}
return flag;
}
using bs = bitset <4103>;
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m, k; cin >> n >> m >> k;
vector <bs> b(n);
for ( int i = 0; i < n; i++ ){
string s; cin >> s;
for ( int j = 0; j < m; j++ ){
if ( s[j] == 'C' ) b[i][j] = 1;
}
}
for ( int i = 0; i < n; i++ ){
bool bad = false;
for ( int j = 0; j < n; j++ ){
if ( i == j ) continue;
if ( (int)(b[i] ^ b[j]).count() != k ){
bad = 1; break;
}
}
if ( !bad ) return cout << i + 1 << "\n", 0;
}
assert(false);
cout << '\n';
}
