import math


def check_line(line, start, square_size, current_count):
    dict = {'X': 0, 'O': 0}
    for j in range(start, start + current_count):
        dict[line[j]] += 1

    smaller_square = (square_size - 2) * (square_size - 2)
    if dict['X'] == smaller_square or dict['O'] == smaller_square:
        return True

    return False


def some_func(line, line_size):
    count = 0
    for i in range(3, math.floor(math.sqrt(line_size)) + 1):
        i_sqr = i * i
        for line_start in range(line_size - i_sqr + 1):
            res = check_line(line, line_start, i, i_sqr)
            if res:
                count += 1

    return count


if __name__ == '__main__':
    count = int(input())
    line = input()
    res = some_func(line, count)
    print(res)