#include <bits/stdc++.h>
#include <assert.h>
#include <unordered_map>
using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector < long long > vll;
typedef pair < long long, long long > pll;
typedef pair < int, int > pii;
typedef vector < int > vii;

#define csl ios_base::sync_with_stdio(false); cin.tie(NULL)
#define l(x) (((x) << 1) | 1)
#define r(x) ((l(x)) + 1)
#define mp make_pair
#define fst first
#define snd second

ll t, n, u, v, m, q, r, ql, qr, k, l, s, x, y, w, c;
const int N = 1e6 + 500;
const long long mod = 1e9 + 7;
const long long INF = 1LL << 57LL;
const bool JUDGE = false;
vii adj[N];
bool vis[N], partcyc[N];
int nxt[N];
ll len[N], tl[N];
ll ans = 0;
ll ret = 0;
inline void calc(int v, int p) {
    tl[v] = 0;
    //cout << v << '\n';
    vis[v] = true;
    ll besta = 0;
    ll bestb = 0;
    for (int i = 0; i < adj[v].size(); ++i) {
        int u = adj[v][i];
        if (u == p || partcyc[u]) continue;
        calc(u, v);
        tl[v] = max(tl[v], tl[u] + len[u]);
        ll temp = tl[u] + len[u];
        if (temp > besta) swap(besta, temp);
        if (temp > bestb) bestb = temp;
    }
    ret = max(ret, besta + bestb);
}

inline ll solve (int v) {
    int start = -1;
    while (!vis[v]) {
        vis[v] = true;
        v = nxt[v];
    }
    ret = 0;
    start = v;
    ll csum = len[v];
    partcyc[v] = true;
    v = nxt[v];
    while (v != start) {
        //cout << v << '\n';
        csum += len[v];
        partcyc[v] = true;
        v = nxt[v];
    }
    //cout << start << ' ';
    calc(v, - 1);
    v = nxt[v];
    while (v != start) {
        calc(v, -1);
        v = nxt[v];
    }
    ll x = tl[start];
    ll y = tl[start] + csum - len[start];
    v = start;
    x += len[v];
    v = nxt[v];
    for (; v != start; v = nxt[v]) {
        ret = max(ret, x + tl[v]);
        ret = max(ret, y + tl[v]);
        x = max(x, tl[v]);
        y = max(y, tl[v] + csum);
        x += len[v];
        y -= len[v];
    }
    //cout << ret << '\n';
    return ret;
}
int main(){
    csl;
    if (JUDGE) {
        freopen("in.txt", "r", stdin);
        freopen("out.txt", "w", stdout);
    }
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        cin >> v >> c;
        u = i;
        nxt[i] = v;
        len[i] = c;
        adj[v].push_back(u);
    }
    for (int i = 1; i <= n; ++i) {
        if (!vis[i]) ans += solve(i);
    }
    cout << ans << '\n';
    return 0;
}