#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
#define l(a, b, i) for (ll i = a; i < b; i++)
#define rl(a, b, i) for (ll i = a; i >= b; i--)
#define vpair vector<pair<ll, ll>>
#define inf LLONG_MAX
#define ninf LLONG_MIN
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
ll N, M; cin >> N >> M; vector<ll> sz(N + 1, 0), val(N + 1, 0), frame(M + 1, 0);
vector<pair<ll, ll>> pic(N + 1, {0, 0});
l(1, N + 1, i) {
cin >> sz[i] >> val[i];
pic[i] = {val[i], sz[i]};
}
l(1, M + 1, i) cin >> frame[i];
sort(frame.rbegin(), frame.rend() - 1); // sort theo decreasing frame size
sort(pic.rbegin(), pic.rend() - 1); // sort theo decreasing val ^^
ll ptr = 1; // keep track xem mình đang ở cái frame nào rùi
ll cnt = 0;
l(1, N + 1, i) { // iterate qua pics nhee
if (ptr > M) break; // vượt max frame mình có rùi :>
if (pic[i].second <= frame[ptr]) {
ptr++;
cnt++;
}
}
cout << cnt;
}
