#pragma GCC optimize("O3,inline")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int ll
using ii = pair<int, int>;
using iii = pair<int, ii>;
constexpr int MAXN = 200'000 + 5;
constexpr int INF = 1e18 + 5;
signed main() {
ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
int C, P; cin >> C >> P;
vector<ii> contests(C);
vector<ii> problems(P);
for (int i = 0; i < C; ++i) cin >> contests[i].first >> contests[i].second;
for (int i = 0; i < P; ++i) cin >> problems[i].first >> problems[i].second;
sort(contests.begin(), contests.end()); sort(problems.begin(), problems.end());
int mx = -INF;
int ptr = -1;
int ans = 0;
for (int i = 0; i < P; ++i) {
while (ptr + 1 < C && contests[ptr + 1].first <= problems[i].first) {
ptr++;
mx = max(mx, contests[ptr].second);
}
if (mx > problems[i].second) ans += mx - problems[i].second;
}
cout << ans;
}
