#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

template<int MOD>
class ModInt {
public:
    ModInt() :value(0) {}
    ModInt(long long val) :value((int)(val<0 ? MOD + val%MOD : val%MOD)) { }

    ModInt& operator+=(ModInt that) {
        value = value + that.value;
        if (value >= MOD)value -= MOD;
        return *this;
    }
    ModInt& operator-=(ModInt that) {
        value -= that.value;
        if (value<0)value += MOD;
        return *this;
    }
    ModInt& operator*=(ModInt that) {
        value = (int)((long long)value * that.value % MOD);
        return *this;
    }
    ModInt &operator/=(ModInt that) {
        return *this *= that.inverse();
    }
    ModInt operator+(ModInt that) const {
        return ModInt(*this) += that;
    }
    ModInt operator-(ModInt that) const {
        return ModInt(*this) -= that;
    }
    ModInt operator*(ModInt that) const {
        return ModInt(*this) *= that;
    }
    ModInt operator/(ModInt that) const {
        return ModInt(*this) /= that;
    }
    ModInt pow(long long k) const {
        if (value == 0)return 0;
        ModInt n = *this, res = 1;
        while (k) {
            if (k & 1)res *= n;
            n *= n;
            k >>= 1;
        }
        return res;
    }
    ModInt inverse() const {
        long long a = value, 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);
        }
        return ModInt(u);
    }
    int toi() const { return value; }

private:
    int value;
};
typedef ModInt<1000000007> mint;
ostream& operator<<(ostream& os, const mint& x) {
    os << x.toi();
    return os;
}

int N, cnt[200005];
vi G[200005];
typedef array<mint, 3> A;
deque<A> dp[200005], EMP;

void f(int u, int dep) {
    cnt[dep]++;
    if (sz(G[u]) == 0) {
        dp[u].push_back(A());
        rep(i, 2)dp[u][0][i] = 1;
        return;
    }

    int id = -1, ma = 0, mama = 0;
    each(v, G[u]) {
        f(v, dep+1);
        if (sz(dp[v]) > ma) {
            ma = sz(dp[v]);
            id = v;
        }
    }
    each(v, G[u])if (v != id)smax(mama, sz(dp[v]));
    rep(i, mama)dp[id][i][2] = 0;

    auto &res = dp[id];
    each(v, G[u])if (v != id) {
        rep(d, sz(dp[v])) {
            auto x = res[d], y = dp[v][d];
            A nex;
            rep(i, 3)rep(j, 2)nex[min(2, i + j)] += x[i] * y[j];
            res[d] = nex;
        }
        
    }
    rep(i, mama)res[i][0] += res[i][2];
    res.emplace_front(A());
    res[0][0] = res[0][1] = 1;
    swap(dp[id], dp[u]);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> N;
    for (int i = 1; i <= N; ++i) {
        int p; cin >> p;
        G[p].push_back(i);
    }
    f(0, 0);

    mint ans = 0;
    rep(i, sz(dp[0])) {
        ans += dp[0][i][1] * mint(2).pow(N+1-cnt[i]);
    }
    cout << ans << endl;
}


Measured memory_bytes: 186240