vector<int> g[MAXN];
int q[MAXN], dp[MAXN][2];

void calc(int v) {
    int sum1 = q[v], sum2 = 0;
    for (int i : g[v]) {
        calc(i);
        sum1 += dp[i][0];
        sum2 += max(dp[i][0], dp[i][1]);
    }
    dp[v][1] = sum1;
    dp[v][0] = sum2;
}

signed main(void) {
#ifdef LOCAL
    freopen("a.in", "r", stdin);
    freopen("a.out", "w", stdout);
#else
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
#endif
    int n, p, root;
    cin >> n;
    for (int i = 0; i < n; ++i) {
        cin >> p >> q[i], p--;
        if (p >= 0) {
            g[p].push_back(i);
        } else root = i;
    }
    calc(root);
    cout << max(dp[root][0], dp[root][1]);
}