// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx")
// #pragma comment(linker, "/stack:200000000"]

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <unordered_set>
#include <unordered_map>
#include <set>
#include <map>
#include <queue>
#include <deque>
#include <bitset>
#include <stack>
#include <random>
#include <fstream>
#include <sstream>
#include <chrono>

#define fi first
#define se second
#define pb push_back
#define ll long long
#define ld long double
#define hm unordered_map
#define pii pair<int, int>
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define cinv(v) for (auto& x: v) cin >> x
#define fr(i, n) for (int i = 0; i < n; ++i)
#define fl(i, l, n) for (int i = l; i < n; ++i)

#define int ll

using namespace std;

#ifdef __LOCAL
    #define dbg(x) cerr << #x << " : " << x << '\n'
    const int maxn = 20;
#else
    #define dbg(x)
    const int maxn = 2e5 + 20;
#endif

//tg: @galebickosikasa

const ll inf = (ll) 2e9;
const ld pi = asin (1) * 2;
const ld eps = 1e-8;
const ll mod = (ll)1e9 + 7;
const ll ns = 97;

mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());



signed main () {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int m, l, n;
    cin >> m >> l >> n;
    vector<vector<char>> moo (m, vector<char> (n));
    for (auto& v: moo) cinv (v);
    vector<string> goo (n);
    fr (i, n) {
        fr (j, m) {
            goo[i] += moo[j][i];
        }
    }
    // for (auto& x: goo) dbg (x);
    hm <string, int> cnt, lst;
    fr (j, n) {
        auto& s = goo[j];
        string t;
        hm <string, int> local;
        fr (i, sz (s)) {
            if (i % l == 0) {
                ++local[t];
                lst[t] = j;
                t = "";
            }
            t += s[i];
        }
        ++local[t];
        lst[t] = j;
        for (auto& x: local) ++cnt[x.fi];
    }
    // for (auto& x: cnt) {
    //     dbg (x.fi);
    //     dbg (x.se);
    // }
    int mn = inf;
    for (auto& x: cnt) {
        if (x.se == 1) {
            cout << lst[x.fi] + 1;
            exit (0);
        }
    }
    cout << 0;







}