import sys

class Patio:
	def param(self,csuc):
		return ((csuc +3)*4)-4
	def solver(self):
		csuc = 1
		count = 0
		circles = 0
		crosses = 0
		c = 1
		shift = 3
		for i in range(len(self.tiles)):
			if self.tiles[i] == "O":
				circles += 1
			if self.tiles[i] == "X":
				crosses += 1
		for i in range(1, crosses+1):
			csuc = 0
			while self.param(csuc) <= i and (csuc+1)*(csuc+1) <= circles:
				if self.param(csuc) == i:
					count += 1
				count += i - self.param(csuc)
				csuc += 1

		print(count)
	def __init__(self):
		self.input = sys.stdin.read()
		self.input = self.input.split("\n")
		self.tiles = self.input[1]
		self.solver()

p = Patio()