#include <bits/stdc++.h>
using namespace std;
#define a first
#define b second
#define pb push_back
typedef long long llo;
vector<pair<llo,llo>> adj[300001];
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ord tree<pair<llo,llo>,null_type,less<pair<llo,llo>>,rb_tree_tag,tree_order_statistics_node_update>
ord xx[300001];
pair<llo,llo> fun[300001];
llo n,m;
llo cot=0;
llo dfs(llo no){
vector<llo> cur;
for(auto j:adj[no]){
if(j.a>=n){
fun[j.a]={-1,j.b};
xx[j.a].insert({j.b,cot});
cot++;
xx[j.a].insert({j.b,cot});
cot++;
cur.pb(j.a);
}
else{
llo x=dfs(j.a);
cur.pb(x);
llo la2=-1;
while(xx[x].size()+fun[x].a>0){
if(xx[x].size()+fun[x].a==1){
la2=(*(xx[x].find_by_order(xx[x].size()-1))).a;
}
xx[x].erase(xx[x].find_by_order(xx[x].size()-1));
}
llo la=(*(xx[x].find_by_order(xx[x].size()-1))).a;
if(la2==-1){
la2=la;
}
fun[x].b+=j.b;
if(xx[x].size()+fun[x].a==0){
xx[x].erase(xx[x].find_by_order(xx[x].size()-1));
}
else{
while(xx[x].size()+fun[x].a<0){
xx[x].insert({la,cot});
cot++;
}
}
//sum is -1
//xx[x].insert({la,cot});
cot++;
xx[x].insert({la+j.b,cot});
cot++;
xx[x].insert({la2+j.b,cot});
cot++;
/*if(no==1){
cout<<fun[x].a<<":"<<fun[x].b<<endl;
for(auto j:xx[x]){
cout<<j.a<<",";
}
cout<<endl;
}*/
//fun[x].a+=-1;
//fun[x].b+=j.b;
}
}
pair<llo,llo> ma={-1,-1};
for(auto j:cur){
ma=max(ma,{(llo)xx[j].size(),j});
}
for(auto j:cur){
if(j!=ma.b){
for(auto jj:xx[j]){
xx[ma.b].insert(jj);
}
fun[ma.b].a+=fun[j].a;
fun[ma.b].b+=fun[j].b;
}
}
/*cout<<no<<"::"<<ma.b<<endl;
cout<<fun[ma.b].a<<";"<<fun[ma.b].b<<endl;
for(auto j:xx[ma.b]){
cout<<j.a<<",";
}
cout<<endl;*/
return ma.b;
}
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin>>n>>m;
for(llo i=1;i<n+m;i++){
llo aa,bb;
cin>>aa>>bb;
aa--;
adj[aa].pb({i,bb});
}
llo ha=dfs(0);
llo ans=fun[ha].a;
vector<int> ne;
for(auto j:xx[ha]){
ne.pb(j.a);
}
llo val=fun[ha].b;
llo pr=0;
for(int i=0;i<ne.size();i++){
if(fun[ha].a>=0){
break;
}
val+=fun[ha].a*(ne[i]-pr);
pr=ne[i];
fun[ha].a+=1;
}
cout<<val<<endl;
/*cout<<fun[ha].a<<"::"<<fun[ha].b<<endl;
for(auto j:xx[ha]){
cout<<j.a<<",";
}
cout<<endl;
*/
return 0;
}
