#include "bits/stdc++.h"

using namespace std;

using lint = int64_t;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m, k;
    cin>>n>>m>>k;
    vector<pair<string, int>> v(n);
    for(int i = 0;i<n; i++){
        auto &[s, id] = v[i];
        cin>>s;
        id = i + 1;
    }
    {
        vector<int> ids(n);
        iota(ids.begin(), ids.end(), 0);
        mt19937 rng(random_device{}());
        shuffle(ids.begin(), ids.end(), rng);
        auto new_v = v;
        for(int i =0; i<n; i++)
            new_v[i] = v[ids[i]];
        v.swap(new_v); 
    }
    vector<array<int, 4>> cnt(m);
    for(int i=0;i<m; i++){
        cnt[i] = {0};
        for(const auto &[s, id] : v){
            cnt[i][s[i] - 'A']++;
        }
    }
    int goal = (n-1) * k;
    for(int _ =0; _<n; _++){
        const auto &[s, id] = v[_];
        int dif = 0;
        for(int i =0; i<m; i++){
            for(int j =0; j<4; j++){
                if((s[i] - 'A') == j) continue;
                dif += cnt[i][j];
            }
            
        }
        if(dif != goal) continue;
        bool ok = true;
        for(int i = 1; i<n && ok; i++){
            int other = (_ + i) % n;
            const auto &[other_s, other_id] = v[other];

            int cur_dif = 0;
            for(int j = 0; j<m; j++){
                if(s[j] != other_s[j])
                    cur_dif++;
            }
            if(cur_dif != k)
                ok = false;
        }
        if(ok){
            cout<<id<<"\n";
            return 0;
        }

    }
    
    return 0;
}