#include<bits/stdc++.h>
using namespace std;
int n,m,s,b[1000000];
struct node{
    int st,ed;
}a[1000000];
bool cmp(node x,node y){
    if(x.ed==y.ed){
        return x.st<y.st;
    }else{
        return x.ed<y.ed;
    }
} 
int main(){
    freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
      cin>>n>>m;
      for(int i=1;i<=n;i++){
          cin>>a[i].st>>a[i].ed;
      }
      for(int i=1;i<=m;i++){
          cin>>b[i];
      }
      sort(a+1,a+1+n,cmp);
      sort(b+1,b+1+m);
      int j=1;
      for(int i=1;i<=n;){
          if(b[j]<a[i].st)j++;
          if(b[j]<=a[i].ed&&b[j]>=a[i].st){
              s++;
              j++;
              i++;
               
          }
          
          if(j>m){
             break; 
          }
      }
      cout<<s;
      
}