#include <bits/stdc++.h>
#include <bits/extc++.h>
#define int long long
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using namespace std;
const int N = 605, M = 305;
vector<pair<int,int>> adj[N];
int dp[N], to[N], deg[N], ans = 0;
__gnu_pbds::priority_queue<int> pq[N];
void dfs(int u, int p){
for(auto [v,w] : adj[u]){
if(v == p) continue;
dfs(v,u);
pq[u].join(pq[v]);
}
if(u==1) return;
int l = 0, r = 0;
if(deg[u]){
while(--deg[u]){
pq[u].pop();
}
r = pq[u].top();
pq[u].pop();
l = pq[u].top();
pq[u].pop();
}
pq[u].push(l+to[u]);
pq[u].push(r+to[u]);
}
signed main(){
fastio
int n,m;
cin >> n >> m;
for(int i = 2;i <= n;i++){
int p,x;
cin >> p >> x;
to[i] = x;
adj[p].push_back({i,x});
adj[i].push_back({p,x});
deg[p]++;
ans += x;
}
for(int i = 1;i <= m;i++){
int p,x;
cin >> p >> x;
to[n+i] = x;
adj[p].push_back({i+n,x});
adj[i+n].push_back({p,x});
deg[p]++;
ans += x;
}
dfs(1,-1);
while(deg[1]--){
pq[1].pop();
}
while(!pq[1].empty()){
ans -= pq[1].top();
pq[1].pop();
}
cout << ans << "\n";
}
