#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
template<typename T> using Tree = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long int ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
#define fastio ios_base::sync_with_stdio(false); cin.tie(NULL)
#define pb push_back
#define endl '\n'
#define sz(a) (int)a.size()
#define setbits(x) __builtin_popcountll(x)
#define ff first
#define ss second
#define conts continue
#define ceil2(x,y) ((x+y-1)/(y))
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define yes cout << "Yes" << endl
#define no cout << "No" << endl
#define rep(i,n) for(int i = 0; i < n; ++i)
#define rep1(i,n) for(int i = 1; i <= n; ++i)
#define rev(i,s,e) for(int i = s; i >= e; --i)
#define trav(i,a) for(auto &i : a)
template<typename T>
void amin(T &a, T b) {
a = min(a,b);
}
template<typename T>
void amax(T &a, T b) {
a = max(a,b);
}
#ifdef LOCAL
#include "debug.h"
#else
#define debug(x) 42
#endif
/*
*/
const int MOD = 1e9 + 7;
const int N = 1e6 + 5;
const int inf1 = int(1e9) + 5;
const ll inf2 = ll(1e18) + 5;
vector<pll> adj[N];
vector<bool> on_cyc(N,1);
vector<ll> mxd(N);
void dfs1(ll u, ll p){
for(auto [v,w] : adj[u]){
if(v == p or on_cyc[v]) conts;
dfs1(v,u);
amax(mxd[u],mxd[v]+w);
}
}
pll diam;
void dfs2(ll u, ll p, ll d){
pll px = {d,u};
amax(diam,px);
for(auto [v,w] : adj[u]){
if(v == p or on_cyc[v]) conts;
dfs2(v,u,d+w);
}
}
void solve(int test_case)
{
ll n; cin >> n;
vector<ll> a(n+5), b(n+5);
rep1(u,n){
ll v,w; cin >> v >> w;
a[u] = v;
b[u] = w;
adj[u].pb({v,w}), adj[v].pb({u,w});
}
queue<ll> q;
vector<ll> indeg(n+5);
rep1(i,n) indeg[a[i]]++;
rep1(i,n){
if(!indeg[i]){
q.push(i);
}
}
while(!q.empty()){
ll u = q.front();
q.pop();
on_cyc[u] = 0;
ll v = a[u];
indeg[v]--;
if(!indeg[v]){
q.push(v);
}
}
vector<bool> vis(n+5);
ll ans = 0;
rep1(i,n){
if(!on_cyc[i]) conts;
if(vis[i]) conts;
ll j = i;
vector<pll> nodes;
vector<ll> weights;
while(!vis[j]){
vis[j] = 1;
nodes.pb({j,-1});
weights.pb(b[j]);
j = a[j];
}
ll siz = sz(nodes);
rep(j,siz){
nodes[j].ss = weights[(j-1+siz)%siz];
}
vector<ll> p(siz);
rep(j,siz){
p[j] = nodes[j].ss;
if(j) p[j] += p[j-1];
}
ll len = p.back();
ll best = 0, mx1 = -inf2, mx2 = -inf2;
rep(j,siz){
ll u = nodes[j].ff;
dfs1(u,-1);
ll d = mxd[u];
amax(best,d+p[j]+mx1);
amax(best,d-p[j]+mx2+len);
amax(mx1,d-p[j]);
amax(mx2,d+p[j]);
on_cyc[u] = 0;
diam = {-1,-1};
dfs2(u,-1,0);
ll s = diam.ss;
diam = {-1,-1};
dfs2(s,-1,0);
amax(best,diam.ff);
on_cyc[u] = 1;
}
ans += best;
}
cout << ans << endl;
}
int main()
{
fastio;
int t = 1;
// cin >> t;
rep1(i, t) {
solve(i);
}
return 0;
}
