#include <bits/stdc++.h>
#define int long long
using namespace std;
const int mod = 998244353;
const int INF = 1e15;
const int mag = 1000000000;
void solve() {
int c, p;
cin >> c >> p;
vector <pair <int, int> > contest(c), problem(p);
for (int i = 0; i< c; i++) {
cin >> contest[i].first >> contest[i].second;
}
sort (contest.begin(), contest.end());
for (int i = 0; i< p; i++) {
cin >> problem[i].first >> problem[i].second;
}
vector <int> pref(c);
for (int i = 0; i< c; i++) {
if (i==0) {
pref[i]=contest[i].second;
} else {
pref[i]=max(pref[i-1], contest[i].second);
}
}
int ans = 0;
for (int i = 0; i< p; i++) {
int q = problem[i].first, d = problem[i].second;
auto it = upper_bound(contest.begin(), contest.end(), make_pair(q,INF));
if (it!=contest.begin()) {
it--;
int idx = it-contest.begin();
if (pref[idx]>d) {
ans+=pref[idx]-d;
}
}
}
cout << ans << endl;
}
signed main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t=1;
//cin >> t;
while (t--) {
solve();
}
}
