#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
const bool typetest = 0;
const int N = 1e5 + 5;
const ll Inf = 1e17;
int n, m, ans(0);
int c[N], dp[N], last[N];
struct picture
{
int s, v;
bool operator<(const picture &a) const
{
return v > a.v || (v == a.v && s > a.s);
}
} a[N];
void Read()
{
cin >> n >> m;
for (int i = 1; i <= n; ++i)
cin >> a[i].s >> a[i].v;
for (int i = 1; i <= m; ++i)
cin >> c[i];
sort(a + 1, a + n + 1);
sort(c + 1, c + m + 1, greater<int>());
}
void Solve()
{
int ans(0), j(1);
for (int i = 1; i <= m; ++i)
{
while (j <= n && a[j].s > c[i])
++j;
if (j > n)
break;
++j;
++ans;
}
cout << ans;
}
int32_t main()
{
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int t(1);
if (typetest)
cin >> t;
for (int _ = 1; _ <= t; ++_)
{
Read();
Solve();
}
}
