#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=200005,M=200005;
ll n,m;
struct node{
    ll l,r;
}dr[N];
bool cmp(node x,node y){
    if(x.l==y.l){
        return x.r-x.l+1<y.r-y.l+1;
    } 
    return x.l<y.l;
}
int t[M];
int main(){
    freopen("dream.in","r",stdin);
    freopen("dream.out","w",stdout);
    cin>>n>>m;
    for(int i=1;i<=n;i++){
        ll l,r;
        cin>>l>>r;
        dr[i]={l,r};
    }
    for(int i=1;i<=m;i++){
        cin>>t[i];
    }
    sort(dr+1,dr+n+1,cmp);
    sort(t+1,t+m+1);
    ll res=0;
    for(int i=1;i<=n;){
        for(int j=1;j<=m;j++){
            if(t[j]>=dr[i].l&&t[j]<=dr[i].r){
                res++;
                i++;
            }
        }
        break;
    }
    cout<<res;
    return 0;
}