#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;
        }
    }

    dp[n+1][m+1] = 0;
    int mi = min(n,m);

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

    printf("%d\n", dp[n-mi+1][m-mi+1]);


    return 0;
}