#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001

int main(){
   
	
	int n,q;
	cin>>n>>q;
	
	vector<int> a(n),b(q);
	rep(i,n)cin>>a[i];
	rep(i,q)cin>>b[i];
	
	vector d(q+1,vector<int>(n,Inf32));
	d[0][0]=0;
	deque<pair<int,int>> D;
	D.emplace_back(0,0);
	while(D.size()>0){
		int x = D.back().first,y = D.back().second;
		D.pop_back();
		{
			if(y+1<n){
				if(d[x][y+1]>d[x][y]+1){
					d[x][y+1]=d[x][y]+1;
					D.emplace_front(x,y+1);
				}
			}
		}
		{
			if(y-1>=0){
				if(d[x][y-1]>d[x][y]+1){
					d[x][y-1]=d[x][y]+1;
					D.emplace_front(x,y-1);
				}
			}
		}
		if(x!=q && b[x]==a[y]){
			if(d[x+1][y]>d[x][y]){
				d[x+1][y]=d[x][y];
				D.emplace_front(x+1,y);
			}
		}
		
	}
	int ans = Inf32;
	rep(i,n)ans = min(ans,d[q][i]);
	cout<<ans<<endl;
	return 0;
}