#include<bits/stdc++.h>
#define int long long
#define F first
#define S second
#define pb push_back
const int mod=1e9+7;
const int N=2000+10;
using namespace std;//初始化
typedef pair <int, int> pi;
int m,n;
int a[N],b[N],dp[N][N]={0};
void solve(){

	cin>>m>>n;
	for(int i=1;i<=m;i++){
		cin>>a[i];
	}
	for(int i=1;i<=n;i++){
		cin>>b[i];
	}
	for(int i=1;i<=m;i++){
		for(int j=1;j<=n;j++){
			if(a[i]==b[j]||a[i]==1||b[i]==1){
				dp[i][j]=dp[i-1][j-1];
			}
			else{
				dp[i][j]=min(dp[i-1][j],dp[i][j-1])+1;
			}
		}
	}
	cout<<dp[m][n]<<endl;
}
signed main(){
	ios::sync_with_stdio(false);cin.tie(0); cout.tie(0);
	cout << fixed << setprecision(12);//小数保留位数
	int t=1;
//	cin>>t;
	while(t--){
		solve();
	}
	return 0;
}