#include <bits/stdc++.h>

using namespace std;
using ll = long long;

int main(){
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);

    ll N, Q, i, j, ni, nj, alt, C;
    cin >> N >> Q;
    vector<ll> A(N+1), B(Q+1);
    for (int i=1; i<=N; i++) cin >> A[i];
    for (int i=1; i<=Q; i++) cin >> B[i];

    /*
       dist(i, j) = 箱iを参照している状態でj枚目までの写真を撮るまでの最小ステップ数
    */

    deque<pair<ll, ll>> que;
    vector dist(N+1, vector<ll>(Q+1, 1e18));
    dist[1][0] = 0;
    que.push_back({1,0});
    
    while(!que.empty()){
        tie(i, j) = que.front();
        que.pop_front();
        if (i <= N-1){
            ni = i+1;
            nj = j;
            C = 1;
            alt = dist[i][j]+C;
            if (alt<dist[ni][nj]){
                dist[ni][nj] = alt;
                que.push_back({ni, nj});
            }
        }
        if (2 <= i){
            ni = i-1;
            nj = j;
            C = 1;
            alt = dist[i][j]+C;
            if (alt<dist[ni][nj]){
                dist[ni][nj] = alt;
                que.push_back({ni, nj});
            }
        }
        if (j+1<=Q && A[i] == B[j+1]){
            ni = i;
            nj = j+1;
            C = 0;
            alt = dist[i][j]+C;
            if (alt<dist[ni][nj]){
                dist[ni][nj] = alt;
                que.push_front({ni, nj});
            }
        }
    }

    ll ans = 1e18;
    for (int i=1; i<=N; i++) ans = min(ans, dist[i][Q]);
    cout << ans << endl;

    return 0;
}