90分代码如下：

#include <bits/stdc++.h>
using namespace std;
long long n,m,x,a[500005],b[500005],ans;
bool check(long long k) 
{
    b[0]=-1e9,b[m+1]=1e9;
	long long l = 1,r = m,mid;
	while(l+1< r)
	{
		mid = (l + r) / 2;
		if (k < b[mid])
		{
		    r = mid;
		}
		else if(k > b[mid])
		{
		    l = mid;
		}
		else 
		{
		    return 1;
		}
	}
	return 0;
}
int main()
{
	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);
	if(!check(a[n])) 
	{   
	    ans++;
	}
	for(int i = 1;i < n;i++)
	{
		if(!check(a[i]) && check(a[i + 1]))
		{
		    ans++;
		}
	}
	cout << ans;
	return 0;
}