#include <bits/stdc++.h>
#define f first
#define s second
using namespace std;
#define int long long
const int maxn = 1e5 + 69;
int n, m, s[maxn], v[maxn], c[maxn];
signed main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
int tt = 1;
//cin >> tt;
while(tt--) {
cin >> n >> m;
for(int i = 0;i < n;i++)
cin >> s[i] >> v[i];
for(int i = 0;i < m;i++)
cin >> c[i];
vector<int> ord(n);
iota(ord.begin(), ord.end(), 0);
sort(ord.begin(), ord.end(), [&](int i, int j) {
return v[i] < v[j];
});
sort(c, c + m);
int l = 1, r = m, ans = 0;
auto check = [&](int mid) {
int cnt = 0, p = mid;
for(int i = 0;i < n;i++) {
int j = ord[i];
if(p > 0 && s[j] <= c[m - p])
--p, ++cnt;
}
return cnt >= mid;
};
while(l <= r) {
int mid = (l + r) / 2;
if(check(mid)) {
ans = mid;
l = mid + 1;
}
else
r = mid - 1;
}
cout << ans << "\n";
}
return 0;
}
