// 23 - 12 - 23
#include<bits/stdc++.h>
using namespace std;
#define read() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define day() time_t now = time(0);char* x = ctime(&now);cerr<<"Right Now Is : "<<x<<"\n"
#define ii pair<int,int>
#define X first
#define Y second
const long long MAX = (int)1e5 + 5;
const long long INF = (int)1e9;
const long long MOD = (int)1e9 + 7;
int n,m;
ii a[MAX];
int c[MAX];
bool check(int len){
int j = m - len + 1;
for(int i = 1;i <= n;i++){
if(a[i].Y > c[j])continue;
j++;
}
return j > m;
}
signed main(){
read();
cin >> n >> m;
for(int i = 1;i <= n;i++){
cin >> a[i].Y >> a[i].X;
}
for(int i = 1;i <= m;i++)cin >> c[i];
sort(a + 1,a + 1 + n);
sort(c + 1,c + 1 + m);
int l = 1,r = m;
int ans = 0;
while(l <= r){
int mid = l + r >> 1;
if(check(mid)){
ans = mid;
l = mid + 1;
}else r = mid - 1;
}
cout << ans;
}
