N = int(input())
string = input()

a = 3
result = 0

while a ** 2 < N:
    xs, os = 0, 0
    for i in range(a ** 2):
        if string[i] == "X":
            xs += 1
        else:
            os += 1
    if xs == 4 * a - 4 and os == (a - 2) ** 2:
        result += 1
    for i in range(N - a ** 2):
        if string[i] == "X":
            xs -= 1
        else:
            os -= 1
        if string[a ** 2 + i] == "X":
            xs += 1
        else:
            os += 1
        if xs == 4 * a - 4 and os == (a - 2) ** 2:
            result += 1

    a += 1

print(result)