from math import sqrt

n = int(input())
tiles = list(input())

answer = 0
side = 3
while True:
	space = side*side
	if space > n:
		break
	ous = 0
	for i in range(space):
		if tiles[i] == "O":
			ous += 1
	for i in range(space, n):
		if ous > 0 and ous < space:
			if ous == (side-2)*(side-2):
				answer += 1
			if (space - ous) == (side-2)*(side-2):
				answer += 1
		if tiles[i] == "O":
			ous += 1
		if tiles[i-space] == "O":
			ous -= 1
	if ous > 0 and ous < space:
		if ous == (side-2)*(side-2):
			answer += 1
		if (space - ous) == (side-2)*(side-2):
			answer += 1
			
	side += 1

	
print(answer)