#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;
#define pii pair<int,int>
int n, m;
pii a[MAXN];
int c[MAXN];
bool ck(int x)
{
int i = 1;
int j = m - x + 1;
int cnt = 0;
while(i <= n and j <= m)
{
if (a[i].second <= c[j])
{
cnt++;
i++;
j++;
}
else
{
i++;
}
}
return cnt >= x;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin >> n >> m;
for (int i = 1; i <= n; i++)
{
cin >> a[i].second >> a[i].first;
}
for (int i = 1; i <= m; i++)
{
cin >> c[i];
}
sort(a + 1, a + n + 1);
sort(c + 1, c + m + 1);
int l = 0;
int r = m;
int ans = 0;
while(l <= r)
{
int mid = (l + r) / 2;
if (ck(mid))
{
ans = mid;
l = mid + 1;
}
else
{
r = mid - 1;
}
}
cout << ans;
}
