import math

input()

inp = input().strip()
res = 0

for i in range(3, 1 + math.floor(math.sqrt(len(inp)))):
    arr = inp[0:i ** 2]
    num_o = arr.count('O')
    if num_o == (i - 2) ** 2:
        res += 1
    for c in range(len(inp) - (i ** 2)):
        if inp[c] == 'O':
            num_o -= 1
        if inp[c + (i ** 2)] == 'O':
            num_o += 1
        if num_o == (i - 2) ** 2:
            res += 1

print(res)