def swap(list, pos1, pos2):
	tmp = list[pos1]
	list[pos1] = list[pos2]
	list[pos2] = tmp
	return list


N = int(input(""))
nums = []

line = input("")
strlist = line.split(" ")

for i in strlist:
	nums.append(int(i) - 1) 

changed = True;
changes = 0;

while changed:
	changed = False;
	for i, num in enumerate(nums):
		if i != num:	
			nums = swap(nums, i, num)
			changed = True; 
			changes = changes + 1

print(changes)