#include <bits/stdc++.h>
using namespace std;
// #define int long long
#define ll long long
#define pii pair<ll, int>
#define F first
#define S second
#define PB push_back
#define ALL(x) x.begin(), x.end()
#define FOR(i, n) for (int i = 0; i < n; i++)
#define NYOOM ios::sync_with_stdio(0); cin.tie(0);
#define endl '\n'
const int INF = 1e9 + 7;
const ll LLINF = 1ll<<60;
const int maxn = 1e6 + 10;
int n, p[maxn], l[maxn];
short seen[maxn] = {0}; // 0 = unseen, 1 = seeing, 2 = seen
ll val[maxn], cur = 0, re = 0; // val[v][i] = node v connected to i nodes already
// val[v][2] >= val[v][1] >= val[v][0]
bool on_cycle[maxn] = {0};
vector<int> adj[maxn];
void dfs(int v, int p){
val[v] = 0;
ll best = -1, second_best = -1;
for (auto u : adj[v]){
if (on_cycle[u] || u == p) continue;
dfs(u, v);
val[v] = max(val[v], val[u] + l[u]);
if (best == -1) best = val[u] + l[u];
else second_best = max(second_best, val[u] + l[u]);
if (second_best > best) swap(best, second_best);
}
cur = max(cur, best + second_best);
}
void solve(int s, int sz){
int v = s;
// forward
deque<pii> dq; // {val, idx}
ll sum = 0;
FOR(i, sz * 2){
while (!dq.empty() && dq.front().S <= i - sz) dq.pop_front();
if (!dq.empty()) cur = max(cur, dq.front().F + sum + val[v]);
while (!dq.empty() && dq.back().F + sum <= val[v]) dq.pop_back();
dq.push_back({val[v] - sum, i});
sum += l[v];
v = p[v];
}
}
void find_cycle(int s){
int v = s;
while (seen[v] == 0){ // while unseen
seen[v] = 1; v = p[v];
}
if (seen[v] == 1){ // found a cycle
cur = 0; int sz = 0;
while (!on_cycle[v]){
sz++; on_cycle[v] = true; v = p[v];
}
FOR(i, sz){
dfs(v, v); v = p[v];
}
solve(v, sz);
re += cur;
}
v = s;
while (seen[v] != 2){
seen[v] = 2; v = p[v];
}
}
signed main(){
NYOOM;
// freopen("isl.in", "r", stdin);
// freopen("isl.out", "w", stdout);
cin >> n;
for (int i = 1; i <= n; i++){
cin >> p[i] >> l[i];
adj[p[i]].PB(i);
}
for (int i = 1; i <= n; i++){
if (seen[i] != 2) find_cycle(i);
}
cout << re;
}
