Submission #891106

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Source Code Expand

#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<string>
#include<map>
#include<cmath>
#include<queue>	
#include<functional>
#include<climits>
#include<utility>
#include<tuple>
#include<cassert>
#include<stack>
using namespace std;

//define
#define ALL(a) a.begin(),a.end()
#define REP(i,n) for(int i=0;i<n;i++)
#define RREP(i,n) for(int i=n-1;i>=0;i--)
#define debug(x) if(1)cout<<#x<<":"<<x<<endl;
#define DEBUG(x) if(1)cout<<#x<<":"<<x<<endl;
#define ll long long
#define PB push_back
#define LB lower_bound
#define UB upper_bound


//constant
const int MOD = 1000000007;
const int INF = INT_MAX / 3 - 1;
const double EPS = 1e-9;
const int dx4[4] = { 1,0,-1,0 };
const int dy4[4] = { 0,1,0,-1 };
const int dx8[8] = { -1,0,1,-1,1,-1,0,1 };
const int dy8[8] = { -1,-1,-1,0,0,1,1,1 };

//typedef
typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef pair<int, int> pii;


int main() {
	int n;
	cin >> n;
	vi a(n);
	int b;
	REP(i, n) {
		cin >> b;
		a[i] = b - 1;
	}
	int cnt = 0;
	REP(i, n) {
		if (a[a[i]]==i)
			cnt++;


	}
	cout << cnt / 2 << endl;
}

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