#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;

mt19937_64 rnd(time(0));
/*
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC target ("avx2,bmi,bmi2,popcnt,lzcnt")
*/

#define name ""
#define FOR(i,x,n) for(int i = x; i <= n; i++)
#define FOD(i,x,n) for(int i = x; i >= n; i--)
#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
#define endl '\n'
#define pll pair<ll, ll>
#define vi vector<ll>
#define vii vector<pll>
#define Nmax int(1e5) + 50
#define N int(1e5)
#define int ll
#define fi first
#define se second
#define pb push_back
#define time() cerr << endl << "*-------------------*Time: " << 1000.0 * clock() / CLOCKS_PER_SEC << "ms.";
template<typename T> bool maximize(T &res, const T &val) { if(res < val){ res = val; return true; }; return false; }
template<typename T> bool minimize(T &res, const T &val) { if(res > val){ res = val; return true; }; return false; }
const int mod = 1e9 + 7;
const int inf = 1e18;



//------------------------------------------

int n, m, k;
string s[N];
int val[N], f[N][4];

//------------------------------------------

void solve()
{
	cin >> n >> m >> k;
	FOR(i, 1, n)
        val[i] = rnd();
	FOR(i, 1, n)
	{
		cin >> s[i];

		s[i] = " " + s[i];

		FOR(j, 1, m)
            f[j][s[i][j] - 'A'] += val[i];
	}

	int res = 0;

	FOR(i, 1, n)
        res += (m - k) * val[i];

	FOR(i, 1, n)
	{
		int sum = 0;

		FOR(j, 1, m)
            sum += f[j][s[i][j] - 'A'];
		sum -= m * val[i];

		if(sum == res - (m - k) * val[i])
            return cout << i, void();
	}
    return;
}

//------------------------------------------

signed main()
{
    fast;
    /*if(fopen != "");
    {
        freopen(name".inp","r", stdin);
        freopen(name".out", "w", stdout);
    }*/
//------------------------------------------

    solve();

//------------------------------------------

    time();
    return 0;
}
/*

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*/