#include <bits/stdc++.h>
#define ll long long int
#define pll pair<ll, ll>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define F0R(i, n) for(auto i = 0; i < (n); i++)
#define FOR(i, a, b) for(auto i = (a); i <= (b); i++)
#define ROF(i, a, b) for(auto i = (a); i >= (b); i--)
using namespace std;
int main()
{
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
int n, m; cin >> n >> m;
vector<pll> photo(n);
vector<ll> frame(m);
F0R(i, n) cin >> photo[i].S >> photo[i].F;
F0R(i, m) cin >> frame[i];
sort(photo.begin(), photo.end());
sort(frame.begin(), frame.end());
int ans = 0;
int pidx = n - 1, fidx = m - 1;
while(pidx >= 0 && fidx >= 0) {
if(frame[fidx] >= photo[pidx].S) ans++, pidx--, fidx--;
else pidx--;
}
cout << ans;
}
