#include <bits/stdc++.h>
using namespace std;
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n,m; cin >> n >> m;
pair<int,int> risa[n];
int lim[m], dp[n+1]; dp[n] = 0;
for (int i = 0; i < n; i++)
cin >> risa[i].second >> risa[i].first;
for (int i = 0; i < m; i++)
cin >> lim[i];
sort(risa,risa+n), sort(lim,lim+m);
for (int i = n-1; i >= 0; i--) {
int l = 0, r = m-1;
while (l < r) {
int s = (l+r)/2;
if (risa[i].second <= lim[s])
r = s;
else
l = s+1;
}
dp[i] = dp[i+1] + ((risa[i].second <= lim[l] && m-l > dp[i+1]) ? 1 : 0);
}
cout << dp[0] << endl;
return 0;
}
