width = 3
buckets = []
needed = dict()

while True:
    border = width * 4 - 4
    inside = (width-2)**2
    count = border + inside
    width += 2

    if count > 20000:
        break
    buckets.append(count)

    needed[count] = (border, inside)

input()
line = input()


class Count:
    def __init__(self):
        self.x = 0
        self.y = 0

    def sub(self, char):
        self.x -= char == 'X'
        self.y -= char == 'O'

    def add(self, char):
        self.x += char == 'X'
        self.y += char == 'O'

counts = {b: Count() for b in buckets}

seq = 0

for idx, char in enumerate(line):
    for bucket in buckets:
        counts[bucket].add(char)
        if idx >= bucket:
            sub = idx - bucket
            counts[bucket].sub(line[sub])

        need = needed[bucket]

        count = counts[bucket]

        seq += (count.x, count.y) == need or (count.y, count.x) == need


print(seq)


# print(check(len(line) - 1))