#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define mp make_pair
#define P pair<ll, ll>
using namespace std;
const int maxn = 1010;
ll dp[maxn][maxn];
vector<P>v;
ll frames[maxn], n, m;
int main() {
ios_base::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m;
ll sz, va;
for(int i=1;i<=n;i++) {
cin>>sz>>va;
v.pb(mp(va, sz));
}
v.pb(mp(0, 0));
sort(v.begin(), v.end());
for(int i=1;i<=m;i++) {
cin>>frames[i];
}
sort(frames+1, frames+m+1);
for(int i=1;i<=n;i++) {
for(int j=1;j<=m;j++) {
dp[i][j] = max(dp[i-1][j], dp[i][j-1]);
if(v[i].second <= frames[j]) {
dp[i][j] = max(dp[i][j], dp[i-1][j-1] + 1);
}
}
}
cout<<dp[n][m]<<"\n";
return 0;
}
