#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
int n,head[1010101],cnt,in[1010101],cycle[1010101][3];
struct node{
	int v,prep,type;
	long long w;
}edge[2020202];
void add(int u,int v,long long w){
	edge[++cnt] = (node){v,head[u],0,w};
	head[u] = cnt;
}queue<int> q;
deque<long long> q1;
deque<int> q2;
bool visit[1010101],vis[1010101],vis2[1010101];
long long maxdep[1010101],maxdis[1010101],ans;
void dfs(int u,int fa){
	long long second = 0;
	for(int i = head[u];i;i = edge[i].prep){
		int v = edge[i].v,type = edge[i].type;
		if(type) continue;
		if(v==fa) continue;
		dfs(v,u);
		maxdis[u] = max(maxdis[u],maxdis[v]);
		long long w = edge[i].w;
		if(maxdep[u]<=maxdep[v]+w){second = maxdep[u];maxdep[u] = maxdep[v]+w;}
		else if(second<maxdep[v]+w) second = maxdep[v]+w;
	}maxdis[u] = max(maxdis[u],maxdep[u]+second);
}void dfs2(int u,int fa){
	vis[u] = 1;
	if(edge[cycle[u][1]].v==fa) swap(cycle[u][1],cycle[u][2]);
	if(!vis[edge[cycle[u][1]].v]) dfs2(edge[cycle[u][1]].v,u);
}
int main(){
	scanf("%d",&n);
	for(int i = 1;i<=n;i++){
		int v;long long w;
		scanf("%d%lld",&v,&w);
		add(i,v,w);add(v,i,w);
		in[v]++;
	}for(int i = 1;i<=n;i++) if(in[i]==0) q.push(i),visit[i] = 1;
	while(!q.empty()){
		int u = q.front();
		q.pop();
		for(int i = head[u];i;i = edge[i].prep){
			int v = edge[i].v;
			if(visit[v]) continue;
			in[v]--;
			if(in[v]<=0) q.push(v),visit[v] = 1;
		}
	}for(int u = 1;u<=n;u++){
		if(!visit[u]){
			for(int i = head[u];i;i = edge[i].prep){
				int v = edge[i].v;
				if(!visit[v]) edge[i].type = 1,cycle[u][++cycle[u][0]] = i;
			}
		}
	}for(int u = 1;u<=n;u++) if(!visit[u]) dfs(u,0);
	for(int u = 1;u<=n;u++) if(!vis[u]) dfs2(u,0);
	for(int i = 1;i<=n;i++){
		if(visit[i] || vis2[i]) continue;
		int u = i;
		long long minus = 0,sum = 0,res = maxdis[u];
		q1.push_back(0),q2.push_back(u),vis2[u] = 1;
		while(!vis2[edge[cycle[u][1]].v]){
			sum += edge[cycle[u][1]].w;
			long long w = sum+maxdep[edge[cycle[u][1]].v];
			while(!q1.empty() && q1.back()<=w) q1.pop_back(),q2.pop_back();
			q1.push_back(w),q2.push_back(edge[cycle[u][1]].v);
			//printf("%d\n",edge[cycle[u][1]].v);
			u = edge[cycle[u][1]].v;
			res = max(res,maxdis[u]);
			vis2[u] = 1;
			res = max(res,q1.front()+maxdep[i]);
			//printf("%d %d %lld\n",i,q2.front(),q1.front()+maxdep[i]);
		}//printf("\n");
		u = i;
		while(edge[cycle[u][1]].v!=i){
			int v = q2.back();long long w = q1.back();
			if(q2.front()==u) q1.pop_front(),q2.pop_front();
			minus += edge[cycle[u][1]].w;
			int j = cycle[v][1];
			w = w-maxdep[v]+edge[j].w+maxdep[edge[j].v];
			v = edge[j].v;
			u = edge[cycle[u][1]].v;
			while(!q1.empty() && q1.back()<=w) q1.pop_back(),q2.pop_back();
			q1.push_back(w),q2.push_back(v);
			res = max(res,q1.front()-minus+maxdep[u]);
			//printf("%d %d %lld\n",u,q2.front(),q1.front()-minus+maxdep[u]);
		}ans += res;
		//printf("%lld\n",res);
		//printf("%d\n",i);
		while(!q1.empty()) q1.pop_back(),q2.pop_back();
	}printf("%lld\n",ans);
	return 0;
}