use proconio::{input, marker::Usize1};
fn main() {
    input! {
        n: usize,
        mut p: [i64; n],
    }
    let mut d = vec![0; n];
    for i in 0..n {
        p[i] -= 1;
    }
    for i in 0..n {
        if p[i] == -1 {
            continue;
        }
        d[p[i] as usize] += 1;
    }
    let mut s = vec![false; n];
    for i in 0..n {
        if d[i] == 0 {
            if p[i] != -1 && p[p[i] as usize] != -1 {
                s[p[p[i] as usize] as usize] = true;
            }
        }
    }
    let mut cnt = 0;
    for i in 0..n {
        if s[i] {
            cnt += 1;
        }
    }
    println!("{cnt}");
}