#include <bits/stdc++.h>
using namespace std;
#define int              long long int
#define double           long double
#define print(a)         for(auto x : a) cout << x << " "; cout << endl


const int M = 1000000007;
const int N = 3e5+9;
const int INF = 2e9+1;
const int LINF = 2000000000000000001;

inline int power(int a, int b, int mod=M) {
    int x = 1;
    a %= mod;
    while (b) {
        if (b & 1) x = (x * a) % mod; 
        a = (a * a) % mod;
        b >>= 1;
    }
    return x;
}


//_ ***************************** START Below *******************************


// 3 3
// 2 8 7 4 1 3 5 6 9 
// 3 2 5
// 1 4 6
// 8 7 9




vector<int> a;
vector<vector<int>> grid;

int consistency(int m, int n){

    
    unordered_map<int,vector<int> > mp;
    for(int i=0; i<m; i++){
        for(int j=0; j<n; j++){
            mp[grid[i][j]] = {i,j};
        }
    }   
    
    vector<int> rows(m, n);
    vector<int> cols(n, m); 
    
    for(int i=0; i<a.size(); i++){
        int val = a[i]; 
        int x = mp[val][0];
        int y = mp[val][1]; 
        
        rows[x]--;
        if(rows[x] == 0) return i;  
        
        cols[y]--;
        if(cols[y] == 0) return i;
    }   
    
    return -1;
}















int practice(int n){


    return 0;
}





void solve() {
    
    int m, n;
    cin>> m >> n;
    
    a.resize(m*n);
    for(int i=0; i<m*n; i++) cin >> a[i];
    
    grid.resize(m, vector<int>(n));
    for(int i=0; i<m; i++){
    	for(int j=0; j<n; j++){
    		cin >> grid[i][j];
    	}
    }
    
    cout << consistency(m, n) << endl;


}





int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }

    return 0;
}