#include <bits/stdc++.h>
#define N 1050
#define f first
#define s second
using namespace std;
typedef pair<int, int> pii;
typedef long long ll;
pii p[N];
ll n, m, dp[N][N], c[N];
ll solve(int i, int j)
{
if(i > n or j > m) return 0;
if(dp[i][j] != -1) return dp[i][j];
int A = 0, B = solve(i + 1, j), C = solve(i, j + 1);
if(p[i].s <= c[j]) A = solve(i + 1, j + 1) + 1;
return dp[i][j] = max({A, B, C});
}
int main()
{
ios::sync_with_stdio(false); cin.tie(0);
cin>>n>>m;
memset(dp, -1, sizeof dp);
for(int i = 1; i <= n; i++) cin>>p[i].s>>p[i].f;
for(int i = 1; i <= m; i++) cin>>c[i];
sort(c + 1, c + m + 1);
sort(p + 1, p + n + 1);
cout<<solve(1, 1)<<"\n";
}
