#include <bits/stdc++.h>
#define ll long long
using namespace std;
int main(){
ll t,a,b,c,d,e,f,g;
cin>>a>>b;
vector<pair<ll,ll>>vp(a+1,{0,0});
for(int i = 1;i<=a;i++){
cin>>vp[i].first>>vp[i].second;
}
sort(vp.begin(),vp.end());
vector<ll>pr(a+1,0);
for(int i = 1;i<=a;i++){
pr[i] = max(pr[i-1],vp[i].second);
}
ll ans = 0;
for(int i = 0;i<b;i++){
cin>>c>>d;
auto it = upper_bound(vp.begin(),vp.end(),make_pair(c,LLONG_MIN));
it--;
ll idx = it-vp.begin();
if(pr[idx] > d){
ans += pr[idx]-d;
}
}
cout<<ans<<endl;
}
//By Rashid_Hashimzade
