#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
typedef long long ll;
typedef pair<int, int> ii;
const int len = 1e6+5;
int deg[len], n, ccs;
ii par[len];
ll dep[len], best[len];
ll val[2*len], pref[2*len];
vector<int> order[len];
vector<ii> adj[len];
void dfs1(int u, int col){
while (deg[u] == 2){
deg[u] = 1;
order[col].pb(u);
u = par[u].fi;
}
}
void find_spec(){
queue<int> myq;
for (int i = 1; i <= n; i++){
deg[i] = adj[i].size();
if (deg[i] == 1)
myq.push(i);
}
while (!myq.empty()){
int u = myq.front(), p = par[u].fi;
myq.pop();
deg[p]--, deg[u]--;
if (deg[p] == 1)
myq.push(p);
}
ccs = 0;
for (int i = 1; i <= n; i++)
if (deg[i] == 2)
dfs1(i, ccs++);
}
ll dfs2(int u, int p = 0){
ll mx1 = 0, mx2 = 0, ans = 0;
for (auto v: adj[u]){
if (v.fi == p || deg[v.fi])
continue;
ans = max(ans, dfs2(v.fi, u));
dep[u] = max(dep[u], dep[v.fi]+v.se);
if (dep[v.fi]+v.se > mx1)
swap(mx1, mx2), mx1 = dep[v.fi]+v.se;
else if (dep[v.fi]+v.se > mx2)
mx2 = dep[v.fi]+v.se;
}
ans = max(ans, mx1+mx2);
return ans;
}
/*ll dfs2(int st){
vector<int> vec;
stack<int> mys;
mys.push(st);
while (!mys.empty()){
int u = mys.top();
mys.pop();
vec.pb(u);
for (auto v: adj[u])
if (v.fi != par[u].fi && !deg[v.fi])
mys.push(v.fi);
}
ll ans = 0;
reverse(vec.begin(), vec.end());
for (auto u: vec){
ll mx1 = 0, mx2 = 0;
for (auto v: adj[u]){
if (v.fi == par[u].fi || deg[v.fi])
continue;
dep[u] = max(dep[u], dep[v.fi]+v.se);
if (dep[v.fi]+v.se > mx1)
swap(mx1, mx2), mx1 = dep[v.fi]+v.se;
else if (dep[v.fi]+v.se > mx2)
mx2 = dep[v.fi]+v.se;
}
ans = max(ans, mx1+mx2);
}
return ans;
}*/
void find_diam(){
for (int i = 0; i < ccs; i++)
for (auto u: order[i])
best[i] = max(best[i], dfs2(u));
}
ll path(vector<int> &vec){
ll ans = 0;
int m = vec.size();
for (int i = 0; i < 2*m; i++)
val[i] = dep[vec[i%m]];
for (int i = 0; i < 2*m-1; i++)
pref[i+1] = pref[i]+par[vec[i%m]].se;
deque<int> deq;
for (int i = 0; i < 2*m; i++){
while (!deq.empty() && i-deq.front()+1 > m)
deq.pop_front();
if (!deq.empty())
ans = max(ans, pref[i]+val[i] + val[deq.front()]-pref[deq.front()]);
while (!deq.empty() && val[i]-pref[i] >= val[deq.back()]-pref[deq.back()])
deq.pop_back();
deq.push_back(i);
}
return ans;
}
void find_path(){
for (int i = 0; i < ccs; i++)
best[i] = max(best[i], path(order[i]));
}
int main(){
scanf("%d", &n);
for (int i = 1; i <= n; i++){
int p, c;
scanf("%d %d", &p, &c);
adj[i].pb(mp(p, c));
adj[p].pb(mp(i, c));
par[i] = mp(p, c);
}
find_spec();
find_diam();
find_path();
ll ans = 0;
for (int i = 0; i < ccs; i++)
ans += best[i];
printf("%lld\n", ans);
return 0;
}
