#include <bits/stdc++.h>
#define int long long
signed main() {
std::ios::sync_with_stdio(false);
std::cin.tie(nullptr);
int c,p;
std::cin >> c >> p;
std::vector<std::pair<int,int>> contest;
for(int i=0;i<c;i++){
int req,gain;
std::cin >> req >> gain;
contest.push_back({req,gain});
}
std::sort(contest.begin(),contest.end());
std::vector<int> bstReq;
std::vector<int> maxGain;
for(int i=1;i<c;i++){
contest[i].second=std::max(contest[i].second,contest[i-1].second);
bstReq.push_back(contest[i].first);
maxGain.push_back(contest[i].second);
}
//std::reverse(bstReq.begin(),bstReq.end());
//std::reverse(maxGain.begin(),maxGain.end());
int sum=0;
for(int i=0;i<p;i++){
int qual,loss;
std::cin >> qual >> loss;
int idx = std::upper_bound(bstReq.begin(),bstReq.end(),qual)-bstReq.begin()-1;
if(idx<0)continue;
else sum+=std::max((int)0,maxGain[idx]-loss);
}
std::cout << sum;
}
