#include <bits/stdc++.h>
#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2")
#define int long long
#define pii pair<int,int>
#define vi vector<int>
#define ff first
#define ss second
#define sp << " " <<
#define all(x) x.begin(),x.end()
#define big(x) ((int)(x.size()))
using namespace std;
const int MOD = 998244353, LIM = 1e6+1, inf = 2e18,N = 2e5+1;
void solve() {
int n,m,k;
cin >> n >> m >> k;
vector<string> strs(n+1);
stack<int> stk;
auto calcdiff =[&](int i,int j) -> int {
int ans = 0;
for (int p = 0;p<m;p++) {
ans+=strs[i][p] != strs[j][p];
}
return ans;
};
for (int i=1;i<=n;i++) {
cin >> strs[i];
if (!stk.empty() && calcdiff(stk.top(),i) != k) {
stk.pop();
continue;
}
stk.push(i);
}
for (int i=n;i>=1;i--) {
if (!stk.empty() && (stk.top() != i && calcdiff(stk.top(),i) != k)) {
stk.pop();
continue;
}
}
cout << stk.top() << '\n';
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0);
int t = 1;
//cin >> t;
while (t --> 0) solve();
}
