#include <cstdio>
#include <stdio.h>
#include <stdbool.h>
#include <iostream>
#include <map>
#include <vector>
#include <climits>
#include <stack>
#include <string>
#include <queue>
#include <algorithm>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cmath>
#include <cctype>
#include <bitset>
#include <iomanip>
#include <cstring>
#include <numeric>
using namespace std;
#define int long long
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define fi first
#define se second
vector<int> m, c;
vector<priority_queue<int> > pq;
vector<vector<pii> > graph;
void dfs(int node, int p){
if (graph[node].empty()){
m[node]=1;
c[node]=-p;
pq[node].push(p);
pq[node].push(p);
return;
}
for (auto num:graph[node]){
dfs(num.fi, num.se);
m[node]+=m[num.fi];
c[node]+=c[num.fi];
if (pq[node].size()<pq[num.fi].size())swap(pq[node], pq[num.fi]);
while (pq[num.fi].size()){
pq[node].push(pq[num.fi].top());
pq[num.fi].pop();
}
}
while (m[node]>1){
--m[node];
c[node]+=pq[node].top();
pq[node].pop();
}
int a=pq[node].top();
pq[node].pop();
int b=pq[node].top();
pq[node].pop();
pq[node].push(a+p);
pq[node].push(b+p);
c[node]-=p;
}
int32_t main(){
int n, k, a, b;
cin>>n>>k;
graph.resize(n+k+1);
m.resize(n+k+1, 0);
c.resize(n+k+1, 0);
pq.resize(n+k+1);
for (int i=2; i<=n+k; ++i)cin>>a>>b, graph[a].pb(mp(i, b));
dfs(1, 0);
while (m[1]>0){
--m[1];
c[1]+=pq[1].top();
pq[1].pop();
}
cout<<c[1];
}
