#!/bin/python
from utils import parse_values

def get_input():
    raw_input_resistors = input("Enter resistor values separated by spaces or commas: ")
    resistors = parse_values(raw_input_resistors)
    return resistors

def calculate_resistance(resistors):
    return 1 / sum(1 / r for r in resistors)

if __name__ == '__main__':
    try:
        resistors = get_input()
    except ValueError as e:
        print(e)
        exit(1)
    print(f"Total resistance = {calculate_resistance(resistors)} ohms")