import sys
import math

n = int(input())

tiles = list(sys.stdin.readline().rstrip('\n'))

size=3

max_size = int(round(math.sqrt(n),0))

result = 0

for j in range(size, max_size+1):
	x_count = 0
	o_count = 0

	for i in range(n):
		if tiles[i] == 'X':
			x_count +=1
		if tiles[i] == 'O':
			o_count +=1
		if i>=j*j:
			if tiles[i-j*j] == 'X':
				x_count -=1
			if tiles[i-j*j] == 'O':
				o_count -=1
		if x_count + o_count == j**2:
			if x_count == j**2-(j-2)**2:
				result +=1
				
			if o_count == j**2-(j-2)**2:
				result +=1

print(result)