#include <bits/stdc++.h>
#define fi first
#define se second
///Input format is not always nice, first nodes may not be in the keychain ring
using namespace std;
typedef long long ll;
typedef pair<int,int> ii;
typedef pair<ll, int> li;
int n;
vector<ii> G[1000005];
ll P[1000005];
int ord[1000005];
int a[1000005], L[1000005];
int D[1000005];
int Pct;
bool vis[1000005];
bool incyc[1000005];
ll ANS;
ll ans;
int cyclehead;
void dfs(int root){
int h = root, t = root;
do{
//printf("%d %d\n",h,t);
h = a[a[h]];
t = a[t];
}
while (h != t);
do{
//printf("%d ",t);
ord[Pct++] = t;
incyc[t] = 1;
t = a[t];
}
while (t != h);
}
ll dfs2(int u, int p){
vis[u] = 1;
ll d2 = 0;
ll d = 0;
for (auto v: G[u]){
if (v.fi == p || incyc[v.fi]) continue;
ll nd = dfs2(v.fi,u)+v.se;
if (d <= nd){
d2 = d;
d = nd;
}
else d2 = max(d2,nd);
}
ans = max(ans,d2+d);
return d;
}
void solve(int root){
ans = Pct = 0;
dfs(root);
//printf("at %d\n",root);
reverse(ord,ord+Pct);
for (int i = 0; i < Pct; i++){
P[i] = dfs2(ord[i],-1);
D[i] = L[ord[i]];
//printf("%d: %d %d\n",x.fi,d[x.fi],x.se);
}
if (Pct == 2){
ANS += max(ans,P[0]+P[1]+max(D[0],D[1]));
return ;
}
ll S = 0;
ll Sl = 0;
for (int i = 0; i < Pct; i++){
S += D[i];
}
ll MX = P[0];
ll MX2 = P[0];
for (int i = 1; i < Pct; i++){
ll x = P[i];
//printf("at %lld %lld\n",d[x],Sl[x]);
//printf("MX: %lld + %lld\n",MX,d[x] + Sl[x]);
//printf("MX2: %lld + %lld\n",MX2,S + d[x] - Sl[x]);
Sl += D[i-1];
ans = max(ans, x + Sl + MX);
ans = max(ans, S + x - Sl + MX2);
MX = max(MX, x - Sl);
MX2 = max(MX2, x + Sl);
}
//printf("%lld max\n",ans);
ANS += ans;
return;
}
int main(){
scanf("%d",&n);
int j,_L;
for (int i = 1; i <= n; i++){
scanf("%d%d",&j,&_L);
a[i] = j;
L[i] = _L;
G[i].push_back({j,_L});
G[j].push_back({i,_L});
}
for (int i = 1; i <= n; i++){
if (vis[i] == 0){
solve(i);
}
}
printf("%lld",ANS);
}
