#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define fi first
#define se second
const bool Multitest = 0;
const int N = 1e5 + 10;
pair<int, int> a[N]; int b[N];
int n, m;
void maximize(int& a, int b)
{
if(a < b) a = b;
}
namespace sub1
{
const int Nsub = 1e3 + 10;
int dp[Nsub][Nsub];
void solve()
{
sort(a + 1, a + 1 + n);
sort(b + 1, b + 1 + m);
for(int i = 1 ; i <= m ; i++)
{
for(int j = 1 ; j <= n ; j++)
{
dp[i][j] = dp[i - 1][j - 1] + (a[j].se <= b[i]);
maximize(dp[i][j], dp[i][j - 1]);
}
}
cout << dp[m][n];
}
}
void work()
{
cin >> n >> m;
for(int i = 1 ; i <= n ; i++)
{
cin >> a[i].se >> a[i].fi;
}
for(int i = 1 ; i <= m ; i++) cin >> b[i];
if(n <= 1000 && m <= 1000) sub1::solve();
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0); cout.tie(0);
int q = 1;
if(Multitest) cin >> q;
while(q--) work();
}
