def foo(tiles, a):
    count = 0
    a2 = a**2
    outer = a2 - (a - 2)**2
    inner = a2 - outer
    red = len(list(filter(lambda x: x, tiles[:a2])))
    blue = a2 - red
    
    if red == outer or blue == outer:
        count += 1
    
    
    for i in range(1, len(tiles) - a2 + 1):
        if tiles[i - 1]:
            red -= 1
        else:
            blue -= 1
            
        if tiles[a2 - 1 + i]:
            red += 1
        else:
            blue += 1
        
        
        
        if red == outer or blue == outer:
            count += 1
            
    return count



n = int(input())

tiles = []
for char in input():
    tiles.append(char == "X")
# print(tiles)


result = 0
size = 3
import math
maxsize = int(math.sqrt(len(tiles)))

for size in range(3, maxsize + 1):
    result += foo(tiles, size)

print(result)