#include <iostream>
#include <cstdlib>
#include <string>
#include <set>
#include <map>
#include <algorithm>
#include <bitset>
#include <queue>
#include <math.h>
#include <stack>
#include <vector>
#include <string.h>
#include <random>
typedef long long ll;
const ll MOD = 1e9 + 7, INF = 1e18;
using namespace std;
int n, m, p[1000001], cost[1000001];
bitset <1000000> is_cycle, u, c;
ll d[1000001][2], root[1000000];
ll pref[2000001];
deque < pair <ll, int> > q_max;
vector < pair <int, int> > g[1000001];
pair <int, int> g_un[1000001];
vector < pair <int, int> > cycle[1000001];
void bfs_traverse (ll x)
{
queue <int> q;
q.push (x);
c[x] = 1;
while (!q.empty ())
{
int x = q.front ();
q.pop ();
for (auto to : g[x])
if (!c[to.first])
{
c[to.first] = 1;
q.push (to.first);
}
}
}
bool bfs_cycle (ll x, ll color)
{
while (!u[x])
{
u[x] = 1;
p[g_un[x].first] = x;
cost[g_un[x].first] = g_un[x].second;
if (u[g_un[x].first] == 1) break;
x = g_un[x].first;
}
int v = x;
auto to = g_un[x];
while (v != to.first)
{
cycle[color].emplace_back (v, cost[v]);
is_cycle[v] = true;
v = p[v];
}
cycle[color].emplace_back (to.first, to.second);
is_cycle[to.first] = true;
return true;
}
ll find_diameter (ll x)
{
queue < pair <int, int> > q;
int mx_i = x;
q.push ({x, -1});
c[x] = 1;
while (!q.empty ())
{
int f = q.front ().first;
int p = q.front ().second;
q.pop ();
if (d[mx_i][0] < d[f][0])
mx_i = f;
for (auto to : g[f])
if ((!is_cycle[to.first] || to.first == x) && to.first != p)
{
d[to.first][0] = d[f][0] + to.second;
c[to.first] = 1;
q.push ({to.first, f});
}
}
root[x] = d[mx_i][0];
while (!q.empty ())
q.pop ();
q.push ({mx_i, -1});
int dist = mx_i;
while (!q.empty ())
{
int f = q.front ().first;
int p = q.front ().second;
q.pop ();
if (d[dist][1] < d[f][1])
dist = f;
for (auto to : g[f])
if ((!is_cycle[to.first] || to.first == x) && to.first != p)
{
d[to.first][1] = d[f][1] + to.second;
c[to.first] = 1;
q.push ({to.first, f});
}
}
return d[dist][1];
}
ll process (vector < pair <int, int> > & cycle)
{
ll diameter = 0;
for (auto x : cycle)
diameter = max (diameter, find_diameter (x.first));
ll s = cycle.size ();
for (ll i = 2 * cycle.size () - 1; i >= 0; i--)
pref[i] = cycle[i % s].second + (i != 2 * cycle.size () - 1 ? pref[i+1] : 0);
q_max.clear ();
for (ll i = 0; i < s - 1; i++)
{
while (!q_max.empty () && q_max.back ().first <= pref[i] + root[cycle[i % s].first])
q_max.pop_back ();
q_max.emplace_back (pref[i] + root[cycle[i % s].first], i);
}
for (ll i = s - 1; i < 2 * cycle.size (); i++)
{
ll k = q_max.front ().first;
diameter = max (diameter, k - pref[i] + root[cycle[i % s].first]);
while (!q_max.empty () && q_max.back ().first <= pref[i] + root[cycle[i % s].first])
q_max.pop_back ();
q_max.emplace_back (pref[i] + root[cycle[i % s].first], i);
while (!q_max.empty () && q_max.front ().second <= i - s + 1)
q_max.pop_front ();
}
return diameter;
}
int main ()
{
cin >> n;
for (ll i = 0; i < n; i++)
{
ll x, l;
scanf ("%lld%lld", &x, &l);
g[i].emplace_back (x - 1, l);
g[x - 1].emplace_back (i, l);
g_un[i] = {x - 1, l};
}
ll color = 0;
for (ll i = 0; i < n; i++)
if (!u[i] && !c[i])
{
bfs_cycle (i, ++color);
bfs_traverse (i);
}
ll ans = 0;
for (ll i = 1; i <= color; i++)
ans += process (cycle[i]);
cout << ans;
}
