def input_percentage():
    x = float(input("Enter a percentage as a decimal number from 0 to 1: "))
    while(x < 0 or x > 1):
        print("Invalid Input!")
        x = float(input("Enter a percentage as a decimal number from 0 to 1: "))
    return x

def input_percentage():
    x = float(input("Enter a percentage as a decimal number from 0 to 1: "))
    while(x < 0 or x > 1):
        print("Invalid Input!")
        x = float(input("Enter a percentage as a decimal number from 0 to 1: "))
    return x


def main():
    print("This program will compute weighted average for three exam scores")
    print("Enter the first exam's score")
    exam1_score = input_percentage()
    print("Enter the first exam's weight")
    exam1_weight = input_percentage()
    print("Enter the second exam's score")
    exam2_score = input_percentage()
    print("Enter the second exam's weight")
    exam2_weight = input_percentage()
    print("Enter the third exam's score")
    exam3_score = input_percentage()
    print("Enter the third exam's weight")
    exam3_weight = input_percentage()
    total = exam1_score * exam1_weight + 
            exam2_score * exam2_weight + 
            exam3_score * exam3_weight
    print("Your total score is {}".format(total))


main()