#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
ll n,m;
pair<ll,ll>p[200005];
ll a[200005];
bool check(ll x) {
ll pos=m-x+1;
for (ll i=1; i<=n; i++) {
if (p[i].second<=a[pos]) {
pos++;
if (pos==m+1) {
return true;
}
}
}
return false;
}
ll bs() {
ll ans=0;
ll l=1;
ll r=min(m,n);
while (l<=r) {
ll mid=(l+r)/2;
if (check(mid)) {
ans=mid;
l=mid+1;
} else {
r=mid-1;
}
}
return ans;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL); cout.tie(NULL);
cin >> n >> m;
for (ll i=1; i<=n; i++) {
cin >> p[i].second >> p[i].first;
}
sort(p+1,p+n+1);
for (ll i=1; i<=m; i++) {
cin >> a[i];
}
sort(a+1,a+m+1);
cout << bs();
}
