Submission #891295

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Source Code Expand

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
#include <functional>

using namespace std;
#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
int N;
vector <int > a;

vector <bool> b;



int main()
{

	cin >> N ;
	int ans=0;
	a.resize(N+1);
	b.resize(N+1);

	REP(i,N){
		cin >> a[i];
		b[i] = false;
	}

	REP(i,N){
		if(b[i])
			continue;
		if(a[a[i]] == i){
			ans++;
			b[a[i]] = true;
		}
	}

	cout << ans;





}

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