#include <bits/stdc++.h>
using namespace std;

#define For(i, a, b) for(int i = (a); i < (b); i++)
#define rep(i, n) For(i, 0, n)
#define rFor(i, a, b) for(int i = (a); i >= (b); i--)
#define ALL(v) (v).begin(), (v).end()
#define rALL(v) (v).rbegin(), (v).rend()
#define SZ(v) ((int)(v).size())

using lint = long long;
using ld = long double;

const int INF = 2000000000;
const lint LINF = 1000000000000000000;
// 真上から反時計回り
const int di[] = {-1, 0, 1, 0};
const int dj[] = {0, -1, 0, 1};
const int di8[] = {-1, -1, 0, 1, 1, 1, 0, -1};
const int dj8[] = {0, -1, -1, -1, 0, 1, 1, 1};

struct SetupIo {
    SetupIo() {
        ios::sync_with_stdio(false); cin.tie(nullptr);
        cout << fixed << setprecision(15);
        cerr << fixed << setprecision(15);
    }
} setupio;

template <class T>
bool chmin(T &a, const T &b) {
    return a > b ? a = b, 1 : 0;
}
template <class T>
bool chmax(T &a, const T &b) {
    return a < b ? a = b, 1 : 0; 
}
template <class T>
T mypow(T a, T b) {
    T res = 1;
    while (b) {
        if (b & 1) { res *= a; }
        a *= a; b >>= 1;
    }
    return res;
}
template <class T>
T modpow(T a, T b, T mod) {
    T res = 1;
    while (b) {
        if (b & 1) { res = (res * a) % mod; }
        a = (a * a) % mod; b >>= 1;
    }
    return res;
}

int main() {
    int N;
    cin >> N;
    vector<int> P(N);
    rep(i, N) {
        cin >> P[i];
        P[i]--;
    }
    vector<int> indeg(N, 0);
    rep(i, N) {
        if (P[i] >= 0) {
            indeg[P[i]]++;
        }
    }
    vector<int> ans(N, 0);
    rep(v, N) {
        if (indeg[v] == 0) {
            int nv = P[v];
            if (nv >= 0) {
                int nnv = P[nv];
                if (nnv >= 0) {
                    ans[nnv] = 1;
                }
            }
        }
    }
    cout << accumulate(ALL(ans), 0) << "\n";
}