#include <bits/stdc++.h>
#define Loop(x,l,r) for (ll x = (l); x < (r); ++x)
#define LoopR(x,l,r) for (ll x = (r)-1; x >= (l); --x)
typedef long long ll;
typedef std::pair<int, int> pii;
typedef std::pair<ll , ll > pll;
using namespace std;
const int N = 100'010;
int f[N];
pii p[N];
int n, m;
int main()
{
cin.tie(0) -> sync_with_stdio(false);
cin >> n >> m;
Loop (i,0,n)
cin >> p[i].second >> p[i].first;
Loop (i,0,m)
cin >> f[i];
sort(f, f+m, greater());
sort(p, p+n, greater());
int ans = 0;
for (int i = 0, j = 0; i < m; ++i) {
while (j < n && p[j].second > f[i])
++j;
if (j == n)
break;
++j;
++ans;
}
cout << ans << '\n';
}
