Witch game

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define fbo find_by_order
#define ook order_of_key

typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<int> vi;
typedef long double ld; 
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
typedef set<int>::iterator sit;
typedef map<int,int>::iterator mit;
typedef vector<int>::iterator vit;

ll d[100001];
set<int> adj[100001];
set<ii> edges;
int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	ll n; cin>>n;
	for(int i = 0; i < n; i++)
	{
		int u; cin>>u;
		u--;
		adj[u].insert(i);
		adj[i].insert(u);
		edges.insert(mp(i,u));
		edges.insert(mp(u,i));
		assert(u!=i);
	}
	ll ans = (n*(n-1)*(n-2))/6;
	ll e = int(edges.size())/2;
	ans -= e*(n-2);
	for(int i = 0; i < n; i++)
	{
		ans+=(adj[i].size()*(int(adj[i].size()) -1))/2;
	}
	cout<<ans;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: WRONG ANSWER

Test 5

Group: 1

Verdict: WRONG ANSWER

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: WRONG ANSWER

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER