#include<bits/stdc++.h>
using namespace std;
int a[500005],b[500005],c[500005];
int main(){
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=n;i++)cin>>a[i];
	for(int i=1;i<=m;i++)cin>>b[i];
	sort(b+1,b+m+1);
	int cur=1;
	for (int i = 1; i <= n; ++i) {
	while (b[cur] < a[i])
		++cur;
	if (b[cur] == a[i])
		c[i]=1;
	}
	int k=0,ans=0;
	for(int i=1;i<=n;i++){
		if(!c[i]&&!k){
			k=!c[i];
			ans++;
		}
		else if(c[i]&&k)k=0;
	}
	cout<<ans<<endl;
}