#include <bits/stdc++.h>
using namespace std;
template <typename T1, typename T2>
istream& operator>>(istream& in, pair<T1, T2>& a) {
  in >> a.first >> a.second;
  return in;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& out, pair<T1, T2> a) {
  out << a.first << " " << a.second;
  return out;
}
template <typename T, typename T1>
T amax(T& a, T1 b) {
  if (b > a) a = b;
  return a;
}
template <typename T, typename T1>
T amin(T& a, T1 b) {
  if (b < a) a = b;
  return a;
}
const long long INF = 1e18;
const int32_t M = 1e9 + 7;
const int32_t MM = 998244353;
const long long N = 2e5 + 5;
vector<long long> v[N];
long long a[N];
long long dp[N][2];
void dfs(long long z, long long p) {
  long long s = 0;
  priority_queue<long long> pq;
  for (long long x : v[z]) {
    if (x == p) continue;
    dfs(x, z);
    s += dp[x][0];
    pq.push(dp[x][1] - dp[x][0]);
  }
  dp[z][0] = s;
  dp[z][1] = s + a[z];
  long long l = (long long)((pq).size());
  for (long long i = 1; i < l + 1; i++) {
    s += pq.top();
    pq.pop();
    if (i & 1) {
      amax(dp[z][1], s);
    } else {
      amax(dp[z][0], s);
      amax(dp[z][1], s + a[z]);
    }
  }
}
void solve() {
  long long n;
  cin >> n;
  for (long long i = 1; i < n + 1; i++) {
    long long p;
    cin >> p >> a[i];
    if (p != -1) v[p].push_back(i);
  }
  dfs(1, 0);
  cout << max(dp[1][0], dp[1][1]);
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) solve();
  return 0;
}
