#include <bits/stdc++.h>

using namespace std;
const int N = 2e5 + 10;
using ll = long long;
ll p[N], q[N];
int main() {
    ll n, m;
    cin >> m >> n;
    if (m >= n) {
        for (int i = 1; i <= m; i++) cin >> p[i];
        for (int i = 1; i <= n; i++) cin >> q[i];
    } else {
        for (int i = 1; i <= m; i++) cin >> q[i];
        for (int i = 1; i <= n; i++) cin >> p[i];
        swap(n, m);
    }

    for (int i = 1; i <= m / 2; i++) swap(p[i], p[m - i + 1]);
    for (int i = 1; i <= n / 2; i++) swap(q[i], q[n - i + 1]);

    vector<vector<ll>> dp(m + 2,vector<ll>( n + 2, 1e18) );
    dp[0][0] = 0;
    dp[0][1] = dp[0][1] = 0;
    ll ans = 1e18;

    for(int j = 0; j <= n ; j++) {
        dp[0][j] = 0;
    }
    for (int i = 1; i <= m; i++) {
        dp[i][0] = 0;
        for (int j = 1; j <= n; j++) {
            if( p[i] == q[j])
                dp[i][j] = min(dp[i][j] , dp[i-1][j-1]);
            if(p[i] == 1) {
                dp[i][j] = min(dp[i][j] , dp[i-1][j]);
            }
            if(q[j] == 1) {
                dp[i][j] = min(dp[i][j] , dp[i][j - 1]);
            }
            dp[i][j] = min(dp[i][j],dp[i-1][j] + 1);
            dp[i][j] = min(dp[i][j],dp[i][j - 1] + 1);
//            cout<<dp[i][j]<<" \n"[j==n];
        }
        ans = min(ans,dp[i][n]);
    }
    cout<<ans<<"\n";
}