#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,Q;
map<int,vector<int>> M;
int dp[1030];

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>Q;
	FOR(i,N) {
		cin>>x;
		M[x].push_back(i);
	}
	FOR(i,1020) dp[i]=1<<30;
	dp[0]=0;
	FOR(i,Q) {
		cin>>x;
		priority_queue<pair<int,int>> PQ;
		FOR(j,N) {
			PQ.push({-dp[j],j});
		}
		while(PQ.size()) {
			int co=-PQ.top().first;
			int cur=PQ.top().second;
			PQ.pop();
			if(dp[cur]!=co) continue;
			if(cur&&chmin(dp[cur-1],co+1)) PQ.push({-dp[cur-1],cur-1});
			if(cur+1<N&&chmin(dp[cur+1],co+1)) PQ.push({-dp[cur+1],cur+1});
		}
		int hoge[1010]={};
		FOR(j,N) {
			hoge[j]=dp[j];
			dp[j]=1<<30;
		}
		FORR(a,M[x]) dp[a]=hoge[a];
		
	}
	cout<<*min_element(dp,dp+N)<<endl;
	
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}