#include <bits/stdc++.h>
using namespace std;
const long double pi = 3.14159265359;
const int N = 1e5 + 5;
const int MOD = 1e9 + 7;
int c[N];
vector<int> ans;
vector<int> g[N];
int main() {
  ios_base::sync_with_stdio(0);
  cout.tie(0);
  cin.tie(0);
  ;
  int n;
  cin >> n;
  int r, p;
  for (int i = 0; i < n; ++i) {
    cin >> p >> c[i];
    --p;
    if (p == -2) {
      r = i;
      continue;
    }
    c[i] = !c[i];
    g[p].push_back(i);
  }
  for (int i = 0; i < n; ++i) {
    if (c[i] || i == r) continue;
    bool gd = false;
    for (auto &it : g[i]) {
      if (c[it]) {
        gd = true;
        break;
      }
    }
    if (!gd) ans.push_back(i);
  }
  if (ans.empty())
    cout << -1;
  else {
    for (auto &it : ans) {
      cout << it + 1 << " ";
    }
  }
  return 0;
}
