#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx2")
using namespace std;
#define pb push_back
#define nl '\n'
#define fore(i, y) for(int i = 0; i < y; i++)
#define forr(i, x, y) for(int i = x;i<=y;i++)
#define forn(i, y, x) for(int i = y; i >= x; i--)
mt19937 rng (chrono::steady_clock::now().time_since_epoch().count());
vector<int> encode(char c)
{
vector<int> v(3 , 0);
if(c == 'A')
v[0] = 1;
else if(c == 'C')
v[1] = 1;
else if(c == 'G')
v[2] = 1;
else
{
v = vector<int>(3 , 1);
}
return v;
}
signed main() {
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n , m , k;
cin>>n>>m>>k;
bitset<3 * 4100> bs[n];
vector<int> cnt(n);
vector<int> perm;
fore(i , n) {
string s;
cin >> s;
fore(j, m) {
vector<int> code = encode(s[j]);
forr(l , 3*j , 3*j + 2)
{
if(code[l - 3*j] == 1)
cnt[i]++;
bs[i][l] = code[l - 3*j];
}
}
}
vector<vector<int>> f(n , vector<int>(n , -1));
fore(i , n)
{
perm.clear();
fore(j , n)
{
if(i == j)
continue;
if(abs(cnt[i] - cnt[j]) > 2 * k || cnt[i] + cnt[j] < 2 * k)
continue;
perm.pb(j);
}
shuffle(perm.begin() , perm.end() , rng);
bool acc = 1;
for(auto j : perm)
{
if(f[i][j] == -1 && f[j][i] == -1)
f[i][j] = f[j][i] = (int)(bs[j]^bs[i]).count();
if(f[i][j] != 2*k)
{
acc = 0;
break;
}
}
if(acc)
{
cout<<i + 1<<nl;
return 0;
}
}
}
