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)