Find PI to the Nth (N = precission) Digit

# Bailey-Borwein-Plouffe formula for calculating Pi

N = 15

def calculate_pi():
    pi = 0
    for k in range(0, N):
        dividend = dividend_for_k(k)
        divider = pow(16, k)
        pi += dividend/divider
    return pi
        
        
def dividend_for_k(k):
    k = float(k)
    dividend = 4/(8*k + 1)
    dividend -= 2/(8*k + 4)
    dividend -= 1/(8*k + 5)
    dividend -= 1/(8*k + 6)
    return dividend
    
    
def main():
    print("The program will return Pi with given precision (rounded):", end=" ")
    precision = input()
    while int(precision) < 1 or int(precision) > 15:
        print("Only [1, 15] numbers are acceptable.")
        print("The program will return Pi with given precision (rounded):", end=" ")
        precision = input()
        
    format_string = '%.' + str(precision) + 'f'
    print(format_string % calculate_pi())


if __name__ == "__main__":
    main()