#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define pll pair<ll,ll>
#define ff first
#define ss second
#define pb push_back
using namespace std;
int n,m,k,i,j,ans;
vector<int> t(4*1000005);
void update(int v,int l,int r,int pos,int x){
    if(l==r){t[v]=max(t[v], x); return; }
    int m=(l+r)/2;
    if(pos<=m)update(v*2,l,m,pos,x);
    else update(v*2+1,m+1,r,pos,x);
    t[v]=max(t[v*2],t[v*2+1]);
}
int mn(int v, int tl, int tr, int l, int r){
    if(tl>r || tr<l) return 0;
    if(l<=tl && tr<=r)return t[v];
    int m=(tl+tr)/2;
    return max(mn(v*2,l,m,l,r),mn(v*2+1,m+1,r,l,r));
}
int main() {
cin>>n>>m;
for(k=1; k<=n; k++){
    cin>>i>>j;
    update(1,1,1000000,i,j);
}
//cout<<1; return 0;
t.resize(4*n+5,0);
while(m--){
    int x,y;
    cin>>x>>y;
    ans+=max(0,mn(1,1,1000000,1,x)-y);
}
cout<<ans;
    return 0;
}