#include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
int n,m;
const int MAXN=2e5+10;
struct lst{
    int l;
    int r;
}e[MAXN];
bool cmp(lst a,lst b){
    if(a.r==b.r)return a.l<b.l;
    else return a.r<b.r;
}
int a[MAXN];
int ans;
int main(){
    freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
    cin>>n>>m;
    for(int i=1;i<=n;i++)cin>>e[i].l>>e[i].r;
    sort(e+1,e+n+1,cmp);
    for(int i=1;i<=m;i++)cin>>a[i];
    sort(a+1,a+n+1);
    int h=1;
    for(int i=1;i<=n;i++){
        if((a[h]>=e[i].l)&&(a[h]<=e[i].r)){
            ans++;
            h++;
        }else {
            if(a[h]<e[i].l){
                while(a[h]<e[i].l)h++;
                if(h<=m)ans++;
            }
        }
    }
    cout<<ans<<endl;
    return 0;
}