#include<cstdio>

 #include<cstring>

 #include<iostream>

 #include<algorithm>

 #define rep(i,l,r) for (int i=(l); i<=(r); i++)

 #define For(i,x) for (int i=h[x],k; i; i=nxt[i])

 typedef long long ll;

 using namespace std;

 const int N=;

 ll ans,res,f[N],v1[N],v2[N],u1[N],u2[N];

 int dfn[N],fa[N],pre[N],h[N],a[N],b[N];

 int n,x,w,cnt,tim,tot,to[N<<],val[N<<],nxt[N<<],d[N];

 void add(int u,int v,int w){ to[++cnt]=v; val[cnt]=w; nxt[cnt]=h[u]; h[u]=cnt; }

 void dfs(int x){

     dfn[x]=++tim;

     For(i,x) if ((k=to[i])!=fa[x]){

         if (!dfn[k]) fa[k]=x,pre[k]=val[i],dfs(k);

         else if (dfn[k]>dfn[x]){

             for (int t=k; t!=x; t=fa[t]) a[++tot]=t,d[t]=,b[tot]=pre[t];

             a[++tot]=x; d[x]=; b[tot]=val[i];

         }

     }

 }

 void Dfs(int x,int fa){

     For(i,x) if ((k=to[i])!=fa && !d[k])

         Dfs(k,x),ans=max(ans,f[x]+f[k]+val[i]),f[x]=max(f[x],f[k]+val[i]);

 }

 void DP(int x){

     tot=; ans=; dfs(x); ll sm=,mx=;

     rep(i,,tot) Dfs(a[i],);

     rep(i,,tot) d[a[i]]=;

     rep(i,,tot+) u1[i]=u2[i]=v1[i]=v2[i]=;

     rep(i,,tot){

         sm+=b[i-]; u1[i]=max(u1[i-],f[a[i]]+sm);

         v1[i]=max(v1[i-],f[a[i]]+sm+mx); mx=max(mx,f[a[i]]-sm);

         ans=max(ans,v1[i]);

     }

     int tmp=b[tot]; sm=mx=b[tot]=;

     for (int i=tot; i; i--){

         sm+=b[i]; u2[i]=max(u2[i+],f[a[i]]+sm);

         v2[i]=max(v2[i+],f[a[i]]+sm+mx); mx=max(mx,f[a[i]]-sm);

         ans=max(ans,v2[i]);

     }

     rep(i,,tot-) ans=max(ans,u1[i]+u2[i+]+tmp);

     res+=ans;

 }

 int main(){

     freopen("bzoj1791.in","r",stdin);

     freopen("bzoj1791.out","w",stdout);

     scanf("%d",&n);

     rep(i,,n) scanf("%d%d",&x,&w),add(x,i,w),add(i,x,w);

     rep(i,,n) if (!dfn[i]) DP(i);

     printf("%lld\n",res);

     return ;

 }