Submission #890914

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define FOR(i,k,n) for(int i = (int)(k); i < (int)(n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) a.begin(), a.end()
#define MS(m,v) memset(m,v,sizeof(m))
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> pii;
const int MOD = 1000000007;
const int INF = MOD + 1;
const ld EPS = 1e-12;
template<class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template<class T> T &chmax(T &a, const T &b) { return a = max(a, b); }

/*--------------------template--------------------*/

int main()
{
	cin.sync_with_stdio(false); cout << fixed << setprecision(10);
	int n; cin >> n;
	vi v(n);
	REP(i, n)
	{
		cin >> v[i];
		v[i]--;
	}
	int ans = 0;
	REP(i, n)
	{
		if (i == v[v[i]]) ans++;
	}
	cout << ans / 2 << endl;
	return 0;
}

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