def main():
    input()
    line = input()
    tiles = [op for op in line]
    patios(tiles)



def patios(tiles):
    res = 0
    for i in range(0, len(tiles) - 8):
        n = 3
        j = n**2 - 1
        while i + j < len(tiles):

            if is_correct(tiles, i, j + i):
                res += 1
            n += 1
            j = n**2 - 1
    
    print(res)


def is_correct(ls, i, j):
    x = 0
    o = 0
    for n in range(i, j + 1):
        if ls[n] == "X":
            x += 1
        else:
            o += 1

    return is_good(x,o) or is_good(o,x)


def is_good(x,o):
    side = round((x + o)**(1/2))
    return x == (x + o) - (side - 2)**2


main()