#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;
}
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