#include <bits/stdc++.h>
#define pb push_back
#define pf push_front
using namespace std;
#define F first
#define S second
typedef long long ll;
#define pii pair <int, int>
#define pll pair <ll, ll>
typedef long double ld;
const ll N = 1e5 + 100, M = 4096 + 10, len = 21, inf = 1e18;
const ll mod = 1e9 + 7;
pll a[N];
ll b[N], pos[N];
int main(){
ios::sync_with_stdio(false);
cin.tie(NULL);
ll n, m, ans = 0;
cin >> n >> m;
for(ll i = 1; i <= n; i++){
cin >> a[i].S >> a[i].F;
pos[i] = LLONG_MAX;
}
sort(a + 1, a + n + 1);
for(ll i = 1; i <= m; i++){
cin >> b[i];
}
sort(b + 1, b + 1 + m);
for(ll i = 1; i <= n; i++){
ll from = -1;
//cout << a[i].F << " "<< a[i].S << endl;
for(ll j = 1; j <= m; j++){
if(b[j] >= a[i].S){
from = j;
break;
}
}
if(from != -1){
for(ll j = n - 1; j >= 0; j--){
if(pos[j] == LLONG_MAX) continue;
if(pos[j] < from) pos[j + 1] = min(pos[j + 1], from);
else{
if(pos[j] < m) pos[j + 1] = min(pos[j + 1], pos[j] + 1);
}
}
// cout << i << " "<< from << endl;
// for(ll j = 1; j <= n; j++){
// cout << pos[j] << " ";
// }
// cout << endl;
}
}
for(ll i = 1; i <= n; i++){
if(pos[i] != LLONG_MAX) ans = i;
}
cout << ans;
return 0;
}
