// #pragma GCC diagnostic warnig "-std=c++11"
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize ("O3")
// #pragma GCC optimization ("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
#include <bits/stdc++.h>
using namespace std;
 
#define int long long
#define eb emplace_back
#define mp make_pair
#define pb push_back
#define pp pop_back
#define endl '\n'
#define ff first
#define ss second
#define stop exit(0)
#define sz(x) (int)x.size()
#define pause system("pause")
#define all(x) (x).begin(),(x).end()
#define deb(x) cout << #x << "-" << x  << endl
 
typedef char chr;
typedef string str;
// typedef long long ll;
typedef vector <int> vii;
typedef pair <int,int> pii;
 
const long long INF = LLONG_MAX;
const int inf = INT_MAX;
const int mod = 998244353;
const int MOD = 1e9 + 7;
const int dx[] = {0,0,-1,1};
const int dy[] = {-1,1,0,0};
const double PI = 2 * acos(0.0);

const int N = 2e5 + 5;

int n,m,cur,mx,ans;
pii a[N],b[N];

inline void test_case () {  
    
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> a[i].ff >> a[i].ss;
    }
    for (int i = 1; i <= m; i++) {
        cin >> b[i].ff >> b[i].ss;
    }
    sort(a+1,a+1+n);
    sort(b+1,b+1+n);
    cur = 1;
    mx = a[1].ss;
    for (int i = 1; i <= m; i++) {
        while (a[cur+1].ff <= b[i].ff) {
            cur++;
            mx = max(mx,a[cur].ss);
        }
        if (mx - b[i].ss > 0) ans += mx - b[i].ss;
    }
    
    cout << ans << endl;

}
 
signed main () {
 
    ios_base :: sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    
    int T = 1;
    // cin >> T;
    while(T--) {
        test_case();
    }
    
    return 0;
 
}