#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define SZ(a) ((int)a.size())
#define ALL(v) v.begin(), v.end()
#define pb push_back

const int N = 1e5 + 5;

string s[N];
int c[N][4];

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int n, m;
    cin >> n >> m;
    ll k;
    cin >> k;


    auto chk = [&](int t) {
        for (int i = 0; i < n; i++)
            if (i != t) {
                int tt = 0;
                for (int j = 0; j < m; j++)
                    if (s[i][j] != s[t][j])
                        tt++;
                if (tt != k)
                    return false;
            }
        return true;
    };

    vector<int> p(n);
    vector<int> rp(n);
    for (int i = 0; i < n; i++)
        p[i] = i;
    mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
    shuffle(ALL(p), rng);
    for (int i = 0; i < n; i++)
        cin >> s[p[i]], rp[p[i]] = i;
    
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            c[j][s[i][j] - 'A']++;

    for (int i = 0; i < n; i++) {
        ll tt = 0;
        for (int j = 0; j < m; j++) {
            tt += n - c[j][s[i][j] - 'A'];
        }
        if (tt != (ll)(n - 1) * k) continue;
        if (chk(i)) {
            cout << rp[i] + 1 << endl;
            return 0;
        }
    }
    assert(0);

}