#include<deque>
#include<queue>
#include<vector>
#include<algorithm>
#include<iostream>
#include<set>
#include<cmath>
#include<tuple>
#include<string>
#include<chrono>
#include<functional>
#include<iterator>
#include<random>
#include<unordered_set>
#include<unordered_map>
#include<array>
#include<map>
#include<bitset>
#include<iomanip>
#include<list>
#include <numeric>
using namespace std;
typedef unsigned long long int ulint;
typedef long long int llint;
typedef long double lldo;
#define mp make_pair
#define mt make_tuple
#define pub push_back
#define puf push_front
#define pob pop_back
#define pof pop_front
#define fir first
#define sec second
#define res resize
#define ins insert
#define era erase
#define RE return 0
//ios::sync_with_stdio(false);
//std::cin.tie(0);
//<< setprecision(20)
const int mod=(int)1e9+7;
const llint big=(llint)(2.19e12+1);
const long double pai=3.141592653589793238462643383279502884197;
const long double ena=2.71828182845904523536;
const long double eps=1e-7;
template <class T,class U>bool mineq(T& a,U b){if(a>b){a=b;return true;}return false;}
template <class T,class U>bool maxeq(T& a,U b){if(a<b){a=b;return true;}return false;}
template <class T> void soun(T& ar)
{sort(ar.begin(),ar.end());ar.erase(unique(ar.begin(),ar.end()),ar.end());}
llint gcd(llint a,llint b){if(a%b==0){return b;}else{return gcd(b,a%b);}}
llint lcm(llint a,llint b){return a/gcd(a,b) *b;}
template<class T,class U> auto LB(T& ve,U in){return lower_bound(ve.begin(),ve.end(),in);}
template<class T,class U> auto UB(T& ve,U in){return upper_bound(ve.begin(),ve.end(),in);}
template<class T,class U> auto LBI(T& ve,U in){return LB(ve,in)-ve.begin();}
template<class T,class U> auto UBI(T& ve,U in){return UB(ve,in)-ve.begin();}
template<class T> void SO(T& ve){sort(ve.begin(),ve.end());}
template<class T> void REV(T& ve){reverse(ve.begin(),ve.end());}
int main(void){
	int n,i;cin>>n;
	vector<int>oya(n);
	vector<llint>dis(n);
	vector<int>koa(n,-1);
	vector<int>kob(n,-1);
	for(i=1;i<n;i++){
		cin>>oya[i];oya[i]--;
		if(koa[oya[i]]==-1){koa[oya[i]]=i;}
		else{kob[oya[i]]=i;}
		cin>>dis[i];
	}
	
	//二分探索!!!
	//マージテク!!!
	//配列長=(小さいほう)
	llint bmax=big,bmin=-1;
	while(bmax-bmin>1){
		llint bgen=(bmax+bmin)/2;
		//cerr<<"bgen="<<bgen<<endl;
		bool can=true;
		vector<vector<pair<llint,llint>>> dp(n);
		//行き,帰り
		for(i=n-1;i>=0;i--){
			int a=koa[i],b=kob[i];
			if(a==-1){dp[i].pub(mp(dis[i],dis[i]));continue;}
			if(dp[a].size()<dp[b].size()){swap(a,b);}
			//この二つをマージしていく
			//あ、そうか尺取りか
			//it.firは単調増加(一方の道)
			//it.secは単調減少(もう一方の道)
			int basA=0,basB=0;
			dp[a].pub(mp(big,0));
			vector<pair<llint,llint>>ma;
			vector<pair<llint,llint>>zi;
			//cerr<<"de"<<a<<" "<<b<<endl;
			while(basA+1<dp[a].size()&&basB<dp[b].size()){
				if(dp[a][basA].fir+dp[b][basB].sec <= bgen){
					if(dp[a][basA+1].fir+dp[b][basB].sec > bgen){
						ma.pub(mp(dp[b][basB].fir+dis[i],dp[a][basA].sec+dis[i]));
						zi.pub(mp(dp[a][basA].sec+dis[i],dp[b][basB].fir+dis[i]));
					}
					basA++;
				}else{basB++;}
			}
			REV(zi);
			//こいつをマージする
			int basm=0,basz=0;
			ma.pub(mp(big,big));
			zi.pub(mp(big,big));
			llint mae=big;
			while(basm+1<ma.size()||basz+1<zi.size()){
				if(ma[basm].fir==zi[basz].fir){
					if(ma[basm].sec>zi[basz].sec){basm++;}
					else{basz++;}
				}
				if(ma[basm].fir<zi[basz].fir){
					if(mae>ma[basm].sec){dp[i].pub(ma[basm]);mae=ma[basm].sec;}
					basm++;
				}
				else{
					if(mae>zi[basz].sec){dp[i].pub(zi[basz]);mae=zi[basz].sec;}
					basz++;
				}
			}
			if(dp[i].size()==0){can=false;break;}
			//cerr<<"i="<<i<<endl;
			//for(auto it:dp[i]){cerr<<"fir="<<it.fir<<" sec="<<it.sec<<endl;}
		}
		if(can){bmax=bgen;}
		else{bmin=bgen;}
	}
	cout<<bmax<<endl;
	RE;
}

Measured memory_bytes: 41444