#include<bits/stdc++.h>

 #define pa pair<int,int>

 #define ll long long

 using namespace std;

 const int maxn=;

 inline ll rd(){

     ll x=;char c=getchar();int neg=;

     while(c<''||c>''){if(c=='-') neg=-;c=getchar();}

     while(c>=''&&c<='') x=x*+c-'',c=getchar();

     return x*neg;

 }

 multiset<int> st;

 int N,M;

 pa cow[maxn],gra[maxn];

 int main(){

     //freopen("1691.in","r",stdin);

     int i,j,k;

     N=rd();M=rd();

     for(i=;i<=N;i++){

         cow[i].first=rd(),cow[i].second=rd();

     }for(i=;i<=M;i++){

         gra[i].first=rd(),gra[i].second=rd();

     }

     sort(cow+,cow+N+);sort(gra+,gra+M+);

     ll ans=;int num=;

     for(i=,j=;i<=M&&num<=N;i++){

         //printf("%d %d\n",i,j);

         for(;cow[j].first<=gra[i].first&&j<=N;j++){

             st.insert(cow[j].second);

         }

         if(st.empty()||(*st.begin())>gra[i].second) continue;

         multiset<int>::iterator it=st.upper_bound(gra[i].second);it--;

         //printf("%d %d %d %d\n",gra[i].first,gra[i].second,*it,it==st.end());

         st.erase(it);ans+=gra[i].first;num++;

     }

     if(num==N) printf("%lld\n",ans);

     else printf("-1\n");

     return ;

 }