Freshman's Database

import sys

if __name__ == '__main__':
    n = int(sys.stdin.readline().strip())

    values = sys.stdin.readline().strip().split()
    visited = [False]*n
    cycle_visited = [False]*n

    count = 0
    for i in range(n):
        if not visited[i]:
            j = i
            cycle_visited = [False]*n

            while True:
                if j >= n or j < 0:
                    break
                if not cycle_visited[j] and not visited[j]:
                    cycle_visited[j] = True
                    j = int(values[j].strip()) - 1
                else:
                    if not visited[j]:
                        count += 1
                    break
            for k in range(n):
                visited[k] = visited[k] or cycle_visited[k]
    print(count)

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: RUNTIME ERROR

Test 4

Verdict: RUNTIME ERROR

Test 5

Verdict: RUNTIME ERROR

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR