Noitapeli

#include <iostream>

const int N = 1e5;
int target[N];
int ins[N];

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

	int n;
	std::cin >> n;

	int t;
	for (int i = 0; i < n; ++i) {
		std::cin >> t;
		--t;
		target[i] = t;
		++ins[t];
	}
	long long ways = 0;
	for (int a = 0; a < n; ++a) {
		for (int b = a+1; b < n; ++b) {
			if (target[a] == b || target[b] == a) { continue; }
			int others = n - 2 - ins[a] - ins[b];
			int first = target[target[a]];
			if (first != a && first != b) {
				--others;
			}
			int second = target[target[b]];
			if ((target[a] != target[b]) && (second != a && second != b)) {
				--others;
			}
			ways += others;
		}
	}
	ways /= 3;
	std::cout << (ways < 0 ? 0 : ways) << "\n";
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 15

Group: 3

Verdict: TIME LIMIT EXCEEDED