#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
// #define int long long
// #define double long double
#define rep(i,n) for (int i=0; i<(int)(n); ++i)
#define rep1(i,n) for (int i=1; i<(int)(n); ++i)
#define repeq(i,n) for (int i=0; i<=(int)(n); ++i)
#define rep1eq(i,n) for (int i=1; i<=(int)(n); ++i)
#define rrep(i,n) for (int i=(int)(n)-1; i>=0; --i)
#define rrep1(i,n) for (int i=(int)(n)-1; i>0; --i)
#define rrepeq(i,n) for (int i=(int)(n); i>=0; --i)
#define rrep1eq(i,n) for (int i=(int)(n); i>0; --i)
#define REP(i,a,b) for (int i=(int)(a); i<=(int)(b); ++i)
#define RREP(i,a,b) for (int i=(int)(a); i>=(int)(b); --i)
#define ALL(a) (a).begin(), (a).end()
#define RALL(a) (a).rbegin(), (a).rend()
using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
template<typename T> using Graph = vector<vector<T>>;
template<typename T> using Spacial = vector<vector<vector<T>>>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
const int MOD = 1e9+7;
const int MOD2 = 998244353;
// const double EPS = 1e-9;
const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};
string interval[2] = {" ", "\n"}; // {" ", "\n"}

template<typename T> struct is_plural : false_type{};
template<typename T1, typename T2> struct is_plural<pair<T1, T2>> : true_type{};
template<typename T> struct is_plural<vector<T>> : true_type{};
template<typename T> struct is_plural<complex<T>> : true_type{};
 
template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << " " << p.second; }
template<typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto itr = vec.begin(); itr != vec.end(); ++itr) is >> *itr; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec) { if (vec.empty()) return os; bool pl = is_plural<T>(); os << vec.front(); for (auto itr = ++vec.begin(); itr != vec.end(); ++itr) os << interval[pl] << *itr; return os; }
 
bool CoutYN(bool a, string y = "Yes", string n = "No") { cout << (a ? y : n) << "\n"; return a; }

template<typename T1, typename T2> inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template<typename T1, typename T2> inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

long long modpow(int a, long long n, int mod = MOD) { long long ret = 1; do { if (n & 1) ret = ret * a % mod; a = 1LL * a * a % mod; } while (n >>= 1); return ret; }

template<typename T> T GCD(T a, T b) { return b ? GCD(b, a%b) : a; }
template<typename T> T LCM(T a, T b) { return a / GCD(a, b) * b; }

template<typename T1, typename T2> bool CompareBySecond(pair<T1, T2> a, pair<T1, T2> b) { return a.second != b.second ? a.second < b.second : a.first < b.first; }
// counterclockwise from 12 o'clock direction
template<typename T> bool CompareBySlope(pair<T, T> a, pair<T, T> b) { if (a.first * b.first < 0) return a.first < b.first; if (a.first == 0) return a.second >= 0 || b.first > 0; if (b.first == 0) return b.second < 0 && a.first < 0; return a.second * b.first < a.first * b.second; }


/* -------- <templates end> -------- */


long long modinv(long long a, long long mod = MOD) {
  long long b = mod, u = 1, v = 0;
  while (b) {
    long long t = a / b;
    a -= t * b; swap(a, b);
    u -= t * v; swap(u, v);
  }
  u %= mod;
  if (u < 0) u += mod;
  return u;
}

void dfs(Graph<int> &children, vi &ancestor, vi &depth, int v) {
  if (children[v].size() == 1) {
    auto &nv = children[v][0];
    ancestor[nv] = ancestor[v];
    depth[nv] = depth[v] + 1;
    dfs(children, ancestor, depth, nv);
    return;
  }
  for (auto &nv : children[v]) {
    ancestor[nv] = v;
    depth[nv] = depth[v] + 1;
    dfs(children, ancestor, depth, nv);
  }
}

void solve() {
  int n; cin >> n;
  vi parent(n+1); parent[0] = -1;
  Graph<int> children(n+1);
  rep1eq(i,n) {
    int p; cin >> p;
    parent[i] = p;
    children[p].emplace_back(i);
  }

  vi ancestor(n+1), depth(n+1);
  ancestor[0] = -1, depth[0] = 0;
  dfs(children, ancestor, depth, 0);

  int MAX = *max_element(ALL(depth));
  Graph<int> same(MAX+1);
  repeq(i,n) same[depth[i]].emplace_back(i);

  ll ans = modpow(2, n);

  rep1eq(i,MAX) {
    map<pii, vector<pii>> mp;
    for (auto &v : same[i]) {
      int p = ancestor[v];
      mp[{depth[p], p}].emplace_back(1, 1);
    }

    while (!mp.empty()) {
      auto key = mp.rbegin()->first;

      ll product = 1, OK = 0, NG = 1;
      vi zero;

      for (auto &p : mp[key]) {
        if (p.second == 0) zero.emplace_back(p.first);
        else product = product * p.second % MOD;
        NG = NG * (p.first + p.second) % MOD;
      }

      if (zero.empty()) {
        for (auto &p : mp[key]) {
          OK += product * (modinv(p.second) * p.first % MOD) % MOD;
        }
        OK %= MOD;
      } else if (zero.size() == 1) {
        OK = product * zero[0] % MOD;
      }

      NG -= OK;
      if (NG < 0) NG += MOD;

      int nv = ancestor[key.second];

      if (nv == -1) {
        ans += OK * modpow(2, n+1 - same[i].size()) % MOD;
        break;
      }

      mp[{depth[nv], nv}].emplace_back(OK, NG);
      mp.erase(key);
    }
  }

  cout << ans % MOD << endl;
}


/* -------- <programs end> -------- */


signed main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(10);
  solve();
  return 0;
}


Measured memory_bytes: 24448