input()
tiles = input()

BLACK = "X"
WHITE = "O"

counts = [(0,0)]
result = 0

def is_correct(j, blacks, whites):
    return blacks == 4 * (j - 1) and whites == (j - 2) ** 2

for tile in tiles:
    prev_b, prev_w = counts[-1]
    if tile == BLACK:
        counts.append((prev_b + 1, prev_w))
    else:
        counts.append((prev_b, prev_w + 1))

# print(counts)

for i in range(1, len(counts)):
    j = 3
    while i - (j ** 2) >= 0:
        current_b, current_w = counts[i]
        prev_b, prev_w = counts[i - (j ** 2)]
        diff_b, diff_w = current_b - prev_b, current_w - prev_w

        if is_correct(j, diff_b, diff_w):
            result += 1

        j += 1

print(result)