input()
tiles = input()

BLACK = "X"
WHITE = "O"

counts = []
black = 0
white = 0
result = 0

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

for tile in tiles:
    if tile == BLACK:
        black += 1
    else:
        white += 1
    counts.append((black, white))

counts.append((0, 0))

for i in range(len(tiles)):
    j = 3
    while (j ** 2) - 1 <= i:
        # print(i, i - ((j ** 2)))
        current_b, current_w = counts[i]
        current_b -= counts[i - (j ** 2)][0]
        current_w -= counts[i - (j ** 2)][1]
        if is_correct(j, current_b, current_w):
            result += 1

        j += 1

print(result)