Submission #6906541

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

#define rep(i, n) for (int i = 0; i < (int)n; ++i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define each(i,c) for(__typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define all(v) v.begin(), v.end()
#define mset(a, n) memset(a, n, sizeof(a))

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;

const int INF = 1000000000;
const int MOD = 1000000007;
const double eps = 1e-9;

int main(int argc, char *argv[]) {
    // cin.tie(0);
    // ios::sync_with_stdio(false);
    int N; cin >> N;
    vector<int> a(N);
    rep(i, N) cin >> a[i], a[i]--;

    int ans = 0;
    rep(i, N) {
        int j = a[i];
        if (i == a[j]) ans++;
    }
    cout << ans / 2 << endl;
    return 0;
}

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