minmaxpair.cpp

#include<bits/stdc++.h>
using namespace std;
const int maxn = 5e5+10;

int n, a[maxn];

int main() {
    ios::sync_with_stdio(false); cin.tie(0);

    cin >> n;
    for(int i = 1; i <= n; i++) {
        cin >> a[i];
    }

    long long resp = 0;
    int Q = 0;
    for(int i = 1; i <= n; i++) {
        if(a[i] == i) Q++;
    }
    resp+= (long long) Q*(Q-1)/2;

    for(int i = 1; i <= n; i++) {
        if(a[i] > i && a[a[i]] == i) resp++;
    }
    cout << resp << endl;
}