#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define fi first
#define se second
#define vi vector<int>
#define vll vector<long long>
#define pii pair<int, int>
#define pll pair<long long, long long>
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
mt19937_64 rng64(chrono::high_resolution_clock::now().time_since_epoch().count());
inline int rand(int l,int r){return uniform_int_distribution<int>(l, r)(rng);}
inline ll rand(ll l,ll r){return uniform_int_distribution<ll>(l, r)(rng64);}
#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif
struct custom_hash {
static uint64_t splitmix64(uint64_t x) {
x += 0x9e3779b97f4a7c15;
x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
return x ^ (x >> 31);
}
size_t operator()(uint64_t x) const {
static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
return splitmix64(x + FIXED_RANDOM);
}
};
const int MAXN = 4200;
string a[MAXN];
int cnt[MAXN][40];
int n, m, k;
vi e;
bool check(int ind){
shuffle(all(e), rng);
for(auto ele : e){
if(ele == ind){
continue;
}
int l = 0;
for(int j = 0; j < m; j++){
if(a[ele][j] != a[ind][j]){
l++;
}
}
if(l != k){
return false;
}
}
return true;
}
int main(){
ios_base::sync_with_stdio(0);
cin.tie(NULL);
cout.tie(NULL);
cin >> n >> m >> k;
for(int i = 1; i <= n; i++){
cin >> a[i];
for(int j = 0; j < m; j++){
cnt[j][a[i][j] - 'A']++;
}
}
vi p;
for(int i = 1; i <= n; i++){
p.pb(i);
}
shuffle(all(p), rng);
e = p;
int wsk = 0;
while(true){
int i = p[wsk];
wsk++;
int sum = 0;
for(int j = 0; j < m; j++){
sum += (n - cnt[j][a[i][j] - 'A']);
}
if(sum != (n - 1) * k){
continue;
}
if(check(i)){
cout << i << '\n';
return 0;
}
}
return 0;
}
