#include<bits/stdc++.h>
#define newl '\n'
const int N = 3e5 + 10;
const int V = 1e7 + 10;
const long long INF = 1e18;
const long long M = 1e9 + 7;
///had to spent my whole morning messing with deimos calculator to solve (pls be right,pls be right)
long long w[N + 1],au[N + 1],bu[N + 1],n,m;
std::multiset<long long> slope[N + 1];
std::vector<int> adj[N + 1];
void readData(){
std::cin >> n >> m;
for(int i = 2;i <= n;++i){
long long p;
std::cin >> p >> w[i];
adj[p].emplace_back(i);
}
for(int i = 1;i <= m;++i){
long long p;
std::cin >> p >> w[n + i];
adj[p].emplace_back(n + i);
}
}
long long eval(long long cnt,long long a,long long b,const std::multiset<long long> &s){
///evaluate the function at slope changing point position (int)s.size() - cnt + 1 /// 1 index
long long last = *s.rbegin();
long long ans = a * last + b;
auto it = s.rbegin();
int i = 1;
while(i < cnt){
ans -= (a - i) * (*it - *next(it));
it = next(it);
++i;
}
return ans;
}
long long opt(long long a,long long b,const std::multiset<long long> &s){
assert(a > 0);
return eval(a,a,b,s);
}
void fix(long long &a,long long &b,std::multiset<long long> &s){
long long opt_y = opt(a,b,s);
while((int)s.size() > 2){
s.erase(s.begin());
s.erase(prev(s.end()));
}
a = 1;
b = opt_y - *s.rbegin();
}
///opt_y = 1 * x - b
///-b = -x + opt_y
///b = opt_y - x
void get_size(int u = 1){
for(int v : adj[u]){
w[v] += w[u];
get_size(v);
}
}
void dfs(int u = 1){
int heavy = 0;
for(int v : adj[u]){
dfs(v);
if(slope[v].size() > slope[heavy].size()){
heavy = v;
}
}
if(heavy == 0){
au[u] = 1;
bu[u] -= w[u];
slope[u].insert(w[u]);
slope[u].insert(w[u]);
}else{
au[u] = au[heavy];
bu[u] = bu[heavy];
slope[u].swap(slope[heavy]);
for(int v : adj[u]){
if(v == heavy){
continue;
}
for(long long val : slope[v]){
slope[u].insert(val);
}
au[u] += au[v];
bu[u] += bu[v];
}
// if(u == 1){
// std::cout << au[u] << " " << bu[u] << " " << slope[u].size() << newl;
// }
fix(au[u],bu[u],slope[u]);
}
}
int main(){
std::ios_base::sync_with_stdio(false);
std::cin.tie(nullptr);std::cout.tie(nullptr);
readData();
get_size();
dfs();
std::cout << opt(au[1],bu[1],slope[1]);
// std::cout << w[2] << newl;
// for(int i = 1;i <= m;++i){
// std::cout << w[n + i] << " ";
// }
// std::cout << newl;
return 0;
}
