#include <bits/stdc++.h>
#include <utility>
using namespace std;
#define int long long
struct line{
int m,n;
vector<int> points;
line(int m,int n,vector<int> points):m(m),n(n),points(points){}
void operator+=(const line &other){
m+=other.m;
n+=other.n;
vector<int> newpoints(points.size()+other.points.size());
merge(points.begin(), points.end(),other.points.begin(), other.points.end(),newpoints.begin());
points = newpoints;
}
};
int n,m;
vector<pair<int,int>> adj[300001];
line dfs(int x,int p){
if(x>n)return {1,-adj[x][0].second,{adj[x][0].second,adj[x][0].second}};
int len = 0;
line curr(0,0,{});
for(auto&i:adj[x]){
if(i.first!=p)curr+=dfs(i.first,x);
else len = i.second;
}
int currsum = curr.n;
int currslope = curr.m;
for(auto i=curr.points.rbegin();i!=curr.points.rend();i++){
currslope--;
if(currslope==-1)break;
currsum+=*i;
}
while(curr.m>1){
curr.m--;
curr.points.erase(--curr.points.end());
}
curr.points[curr.points.size()-1]+=len;
curr.points[curr.points.size()-2]+=len;
curr.n = currsum-curr.points.back();
return curr;
}
int32_t main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
for(int i=2;i<=n+m;i++){
int p,c;cin>>p>>c;
adj[i].emplace_back(p,c);
adj[p].emplace_back(i,c);
}
auto ans = dfs(1,0);
int currsum = ans.n;
int currslope = ans.m;
for(auto i=ans.points.rbegin();i!=ans.points.rend();i++){
currslope--;
if(currslope==-1)break;
currsum+=*i;
}
cout << currsum << '\n';
}
