Submission #1501178

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Source Code Expand

#include<iostream>
#include<iomanip>
#include<math.h>
#include<vector>
#include<algorithm>
#include<set>
#include<map>
#include<queue>
#include<stack>
#include<string>
#include<complex>

#define INF (long long)1000000000
#define MOD 1000000007
#define EPS 1e-8

#define REP(i, m) for(long long i = 0; i < m; ++i)
#define FOR(i, n, m) for(long long i = n; i < m; ++i)
#define ALL(v) v.begin(), v.end()
#define pb push_back

using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
typedef long double ld;

int main() {
	int n;
	cin>>n;
	vector<int> a(n);
	REP(i,n)cin>>a[i];
	int c = 0;
	REP(i,n) {
		if(a[a[i]-1]-1==i)++c;
	}
	cout<<c/2<<endl;
}

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