#include <bits/stdc++.h>
const int MAXN = 2e5 + 5;
int n, root, p[MAXN], mem[MAXN][2], vis[MAXN];
std::vector<int> adj[MAXN], ch[MAXN][2][2];
std::queue<int> order;
int solve(int u, int x) {
  if (mem[u][x] != -1) return mem[u][x];
  if (!vis[u]) {
    for (int v : adj[u]) {
      int a = solve(v, 0), b = solve(v, 1);
      ch[u][a][b].push_back(v);
    }
    vis[u] = 1;
  }
  if (!ch[u][0][0].empty())
    mem[u][x] = 0;
  else if ((ch[u][1][1].size() + ch[u][1][0].size() + x) % 2 == 0)
    mem[u][x] = 1;
  else if (!ch[u][1][1].empty())
    mem[u][x] = 1;
  else
    mem[u][x] = 0;
  return mem[u][x];
}
void reconstruct(int u, int x) {
  for (int v : ch[u][0][1]) reconstruct(v, 1);
  if ((ch[u][1][1].size() + ch[u][1][0].size() + x) % 2 == 0) {
    order.push(u);
    for (int v : ch[u][1][1]) reconstruct(v, 0);
    for (int v : ch[u][1][0]) reconstruct(v, 0);
  } else {
    reconstruct(ch[u][1][1][0], 1);
    order.push(u);
    for (size_t i = 1; i < ch[u][1][1].size(); ++i) {
      reconstruct(ch[u][1][1][i], 0);
    }
    for (int v : ch[u][1][0]) reconstruct(v, 0);
  }
}
int main() {
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) {
    int par;
    scanf("%d", &par);
    if (par == 0) root = i;
    adj[par].push_back(i);
  }
  memset(mem, -1, sizeof mem);
  if (solve(root, 0)) {
    printf("YES\n");
    reconstruct(root, 0);
    for (; !order.empty(); order.pop()) printf("%d ", order.front());
    printf("\n");
  } else {
    printf("NO\n");
  }
}
