///TRAN THAI BAO :3
#include <iostream>
#include <cstdio>
#include <algorithm>
using namespace std;
#define maxN 100007
typedef pair<int, int> pii;
int n, m;
pii pic[maxN];
int fra[maxN];
void solve()
{
cin >> n >> m;
for(int i = 1; i <= n; i++)
cin >> pic[i].second >> pic[i].first;
for(int i = 1; i <= m; i++)
cin >> fra[i];
sort(fra+1, fra+m+1, greater<int>());
sort(pic+1, pic+n+1, greater<pii>());
int i = 1, j = 1, ans = 0;
while(i <= n && j <= m)
{
if(pic[i].second <= fra[j])
{
i++;
j++;
ans++;
}
i++;
}
cout << ans;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
solve();
return 0;
}
