#include <cstdio>
#include <iostream>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
#include <iomanip>
#include <vector>
#include <queue>
#include <map>
#include <set>
#include <stack>
#include <numeric>
using namespace std;
int a[2010], b[2010], dp[2010][2010];
int main()
{
    int n, m;
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n ; ++i)
        scanf("%d", &a[i]);
    for (int i = 1; i <= m ; ++i)
        scanf("%d", &b[i]);

    for (int i = 0; i <= n ; ++i)
    {
        for (int j = 0; j <= m ; ++j)
        {
            dp[i][j] = 1e9;
        }
    }
    reverse(a+1, a+n+1);
    reverse(b+1,b+m+1);
    dp[n+1][m+1] = 0;
    dp[0][0] = dp[1][1] = dp[0][1] = dp[1][0] = 0;
    int ans = 1e9;
    for (int i = 1; i <= n ; ++i)
    {
        for (int j = 1; j <= m ; ++j)
        {
            if(a[i] == b[j] || a[i] == 1|| b[i] == 1)
                dp[i][j] = min(dp[i-1][j-1], dp[i][j]);
            else
                dp[i][j] = min(dp[i-1][j]+1,dp[i][j-1]+1);


            if( i == n || j == m)
            {
                ans = min(ans , dp[i][j]);
            }
        }
    }

    printf("%d\n", ans);
    return 0;
}