#!/bin/python

def solve():
    num = int(input())
    array = list(map(int, input().split()))

    res = 0

    for i, n in enumerate(array):
        if i != n-1:
            for j in range(i + 1, num):
                m = array[j]
                index = j
                if m == i+1:
                    res += 1
                    array[index], array[i] = array[i], array[index]
                    break

    print(res)


def main():
    try:
        while True:
            solve()
    except:
        pass

main()