#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;
const int N = (1 << 20);

vector<int> colState[25];
int n, m, k, mylog2[N]; 
int res;

int lowbit(int x)
{
    return x & (-x);
}

void dfs(int state, int numbers)
{
    if (numbers >= res) return;
    if (state == (1 << m) - 1) 
    {
        res = numbers;
        return;
    }

    int col = -1;
    for (int i = ((1 << m) - 1) ^ state; i; i -= lowbit(i))
    {
        int tempCol = mylog2[lowbit(i)];
        // cout << i << " " << tempCol << endl;
        if (col == -1 || colState[tempCol].size() < colState[col].size()) col = tempCol;
    }
    // cout << col << " " << colState[col].size() << endl;
    if(col == -1) return;

    for (int i = 0; i < colState[col].size(); ++i) dfs(state | colState[col][i], numbers+1);
}

int main()
{
    scanf("%d %d %d", &n ,&m, &k);
    for (int i = 0; i < m; ++i) mylog2[1 << i] = i;
    res = m + 1;

    for (int i = 0; i < n; ++i)
    {
        int tempState = 0;
        for (int j = 0; j < k; ++j)
        {
            int d;
            scanf("%d", &d);
            tempState |= (1 << (d-1));
        }

        for (int j = 0; j < m; ++j)
        {
            if ((tempState >> j) & 1) 
            {
                colState[j].push_back(tempState);
            }
        }
    }

//  for (int i = 0; i < m; ++i) cout << colState[i].size() << " " ;
//  cout << endl;

    dfs(0, 0);

    if (res == m + 1) res = -1;
    printf("%d", res);
    return 0;
}