import math

input()

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

for i in range(3,1+math.ceil(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)