#include <bits/stdc++.h>
using namespace std;
using ll = long long; 
#ifdef LOCAL
#include <debug.h>
#else
#define dbg(...) 0
#define dbgn(...) 0
#endif

int32_t main() {
    cin.tie(0)->sync_with_stdio(0);
    int n; 
    cin >> n; 
    vector<int> p(n), c(n), c2(n), c3(n); 
    for(int i = 0; i < n; i++){
        cin >> p[i]; p[i]--; 
        if(p[i] < 0) continue; 
        c[p[i]]++; 
    }
    for(int i = 0; i < n; i++){
        if(c[i] == 0){
            if(p[i] < 0) continue; 
            c2[p[i]]++; 
        }
    }
    for(int i = 0; i < n; i++){
        if(c2[i]){
            if(p[i] < 0) continue; 
            c3[p[i]]++; 
        }
    }
    dbg(p, c, c2); 
    int ans = 0; 
    for(int i = 0; i < n; i++){
        if(c3[i]) ans++; 
    }
    cout << ans << '\n'; 
    return 0; 
}