#include <bits/stdc++.h>
using namespace std;
#define int long long
#define double long double
#define FOR(i, l, r, d) for(int i=(l); i<=(r); i+=(d))
#define szof(x) ((int)(x).size())
#define vi vector<int>
#define pii pair<int,int>
#define F first
#define S second
#define pb push_back
#define eb emplace_back
#define mkp make_pair
const int INF = 2147483647;
const int LNF = INF*INF;
const int MOD = 1000000007;
const int mod = 998244353;
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("unroll-loops")
const int MAX = 4110;
int n, m, k;
string str[MAX];
int dif[MAX][MAX];
set<int> rem;
int res;
void find_dif(int u, int v){
if(u == v) return;
if(dif[u][v] != -1) return;
int cnt = 0;
FOR(i, 0, m-1, 1){
if(str[u][i] != str[v][i]){
cnt++;
}
}
dif[u][v] = dif[v][u] = cnt;
if(szof(rem)>50 and u!=v and dif[u][v]!=k){
rem.erase(u);
rem.erase(v);
}
}
int randint(int r){
int a = rand();
int b = rand();
return ((a<<14) ^ b) % r;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
srand(time(NULL));
cin>>n>>m>>k;
FOR(i, 1, n, 1){
cin>>str[i];
}
FOR(i, 1, n, 1){
FOR(j, 1, n, 1){
dif[i][j] = -1;
}
}
FOR(i, 1, n, 1){
rem.insert(i);
}
while(szof(rem) > 50){
int u;
int ru = randint(szof(rem));
int v = randint(n) + 1;
auto it = rem.begin();
FOR(i, 1, ru, 1){
it = next(it);
}
u = *it;
find_dif(u, v);
}
for(int i : rem){
bool flag = 1;
FOR(j, 1, n, 1){
find_dif(i, j);
if(i!=j and dif[i][j]!=k){
flag = 0;
}
}
if(flag){
res = i;
}
}
cout<<res<<'\n';
return 0;
}
