#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;
#define pb push_back
#define st first
#define nd second
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int n, m;
cin >> n >> m;
pair<int, int> T[n];
rep(i, n) {
cin >> T[i].nd >> T[i].st;
}
sort(T, T + n);
reverse(T, T + n);
int C[m];
rep(i, m) {
cin >> C[i];
}
sort(C, C + m);
int it = m - 1;
int ans = 0;
rep(i, n) {
if (C[it] >= T[i].nd) {
ans++;
it--;
}
if (it < 0) {
break;
}
}
cout << ans << '\n';
return 0;
}
