// cre : Nguyen Van Tien
#include <bits/stdc++.h>
#define REP(i,a,b) for (int i = a;i<b;++i)
#define FOR(i,a,b) for (int i = a;i>b;--i)
#define STEP(i,a,b,c) for (int i = a;i<b;i+=c)
#define STEPD(i,a,b,c) for (int i = a;i>b;i-=c)
#define ll long long
#define name "TEST"
using namespace std;
/*
---------------------------------
Nguyen Van Tien - vantien1526
Mê cách ngài define
---------------------------------
*/
const int N = 1e5 + 6;
int n,m,C[N],check[N],check1[N];
struct Arr{
int s,v;
} arr[N];
bool cmp(Arr a,Arr b){
if (a.v != b.v) return a.v > b.v;
return a.s > b.s;
}
void sub1(){
sort(arr + 1,arr + n + 1,cmp);
sort(C + 1,C + m + 1);
int cnt = 0;
FOR (i,m,0){
REP (j,1,n+1){
if (arr[j].s <= C[i] && !check1[j] && !check[i]){
cnt++;
check[i] = check1[j] = 1;
break;
}
}
}
cout << cnt;
}
void sub2(){
sort(arr + 1,arr + n + 1,cmp);
sort(C + 1,C + m + 1);
int cnt = 0,ans = m;
REP (i,1,n+1){
int l = 1,r = ans,res = -1;
while (l <= r){
int mid = l + r >> 1;
if (C[mid] >= arr[i].s){
res = mid;
l = mid + 1;
//check = 1;
}
else{
l = mid + 1;
}
}
if (res != -1){
cnt++;
ans = res-1;
}
}
cout << cnt;
}
void solve(){
cin >> n >> m;
REP (i,1,n+1) cin >> arr[i].s >> arr[i].v;
REP (i,1,m+1) cin >> C[i];
//if (n <= 1000 && m <= 1000) sub1();
sub2();
}
int main()
{
ios_base :: sync_with_stdio(0);
cin.tie(0);cout.tie(0);
//freopen(name".INP","r",stdin);
//freopen(name".OUT","w",stdout);
int t ; t = 1 ; REP (i,0,t) solve();
return 0;
}
