APCS

20170304-2

#include<bits/stdc++.h>
#define ll long long
#define fastio ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)

using namespace std;

signed main(){
    fastio;
    vector<ll> tracked, homie;
    ll n, x, y, sum;
    while(cin>>n){
        homie.assign(n+1,0);
        tracked.assign(n+1,0);
        sum=0;
        for(x=0;x<n;x++){
            cin>>homie[x];
        }
        for(x=0;x<n;x++){
            if(tracked[x]){
                continue;
            }
            y=homie[x];
            while(y!=x){
                tracked[y]=1;
                y=homie[y];
            }
            sum++;
        }
        cout<<sum<<'\n';
    }
}