#include<bits/stdc++.h>
using namespace std;
struct rec{
int l,r;
}e[200010];
int n,m;
int t[200010],fail=1;
bool vis[200010];
int ans;
bool cmp(rec a,rec b){return a.l<b.l;}
priority_queue<int,vector<int>,greater<int>>q;
int main()
{
    freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)scanf("%d%d",&e[i].l,&e[i].r);
    for(int i=1;i<=m;i++)scanf("%d",&t[i]);
    sort(e+1,e+n+1,cmp);
    sort(t+1,t+m+1);
    for(int i=1;i<=m;i++)
    {
        while(e[fail].l<=t[i]&&fail<=n)
        {
           q.push(e[fail].r);
           fail++;
        }
        while(!q.empty()&&q.top()<t[i]) q.pop();
        if(q.size())
        {
           ans++;
           q.pop();
        }
    }
    printf("%d",ans);
    return 0;
}