unit converter

print ("Welcome")#welcomes you to the program
again = 0 #sets to 0 to start the program
while again == 0:#loops the program at the end of asking the conversion

        cont = 0
        while cont == 0:
            measurement = input("Do you want to convert length or mass? ")
            measurement = measurement.lower()
            if measurement == "length" or measurement == "mass":
                cont = 1

        cont = 0
        if measurement == "length":
                while cont == 0:
                    length = input("Which unit do you want to convert? inch, foot, yard, or mile? ")
                    length = length.lower()
                    if length == "inch" or length == "foot" or length == "yard" or length == "mile":
                        cont = 1

        cont = 0
        if measurement == "mass":
                while cont == 0:
                    mass = input("Which unit do you want to convert? gram, ounce, pound, or ton? ")
                    mass = mass.lower()
                    if mass == "gram" or mass == "ounce" or mass == "pound" or mass == "ton":
                        cont = 1
#start inches convert
        cont = 0
        if length == "inch":
            while cont == 0:
                try:
                    amount = float(input("How many inches do you want to convert? "))
                    if amount >= 0:
                        print (amount, "inches converts into...")
                        cont = 1
                    elif amount < 0:
                        print ("Positive numbers only")
                except:
                    print ("Numbers only")
            print ("\n")
            print (amount / 12, "feet")
            print (amount / 36, "yards")
            print (amount / 63360, "miles")
            print ("\n")

            cont = 0
            while cont == 0:
                again = input("Do you want to restart? Yes or No ")
                again = again.lower()
                if again == "yes":
                    cont = 1
                    again = 0
                if again == "no":
                    cont = 1
                    print ("Goodbye")
            print ("\n")


#start foot convert
        cont = 0
        if length == "foot":
            while cont == 0:
                try:
                    amount = float(input("How many feet do you want to convert? "))
                    if amount >= 0:
                        print (amount, "feet converts into...")
                        cont = 1
                    elif amount < 0:
                        print ("Positive numbers only")
                except:
                    print ("Numbers only")
            print ("\n")
            print (amount * 12, "inches")
            print (amount / 3, "yards")
            print (amount / 5280, "miles")
            print ("\n")

            cont = 0
            while cont == 0:
                again = input("Do you want to restart? Yes or No ")
                again = again.lower()
                if again == "yes":
                    cont = 1
                    again = 0
                if again == "no":
                    cont = 1
                    print ("Goodbye")
            print ("\n")

#start yard convert
        cont = 0
        if length == "yard":
            while cont == 0:
                try:
                    amount = float(input("How many yards do you want to convert? "))
                    if amount >= 0:
                        print (amount, "yards converts into...")
                        cont = 1
                    elif amount < 0:
                        print ("Positive numbers only")
                except:
                    print ("Numbers only")
            print ("\n")
            print (amount * 36, "inches")
            print (amount * 3, "feet")
            print (amount / 1760, "miles")
            print ("\n")

            cont = 0
            while cont == 0:
                again = input("Do you want to restart? Yes or No ")
                again = again.lower()
                if again == "yes":
                    cont = 1
                    again = 0
                if again == "no":
                    cont = 1
                    print ("Goodbye")
            print ("\n")

#start mile convert
        cont = 0
        if length == "mile":
            while cont == 0:
                try:
                    amount = float(input("How many miles do you want to convert? "))
                    if amount >= 0:
                        print (amount, "miles converts into...")
                        cont = 1
                    elif amount < 0:
                        print ("Positive numbers only")
                except:
                    print ("Numbers only")
            print ("\n")
            print (amount * 63360, "inches")
            print (amount * 5280, "feet")
            print (amount * 1760, "yards")
            print ("\n")

            cont = 0
            while cont == 0:
                again = input("Do you want to restart? Yes or No ")
                again = again.lower()
                if again == "yes":
                    cont = 1
                    again = 0
                if again == "no":
                    cont = 1
                    print ("Goodbye")
            print ("\n")

#start grams convert
        cont = 0
        if mass == "gram":
            while cont == 0:
                try:
                    amount = float(input("How many miles do you want to convert? "))
                    if amount >= 0:
                        print (amount, "miles converts into...")
                        cont = 1
                    elif amount < 0:
                        print ("Positive numbers only")
                except:
                    print ("Numbers only")
            print ("\n")
            print (amount * 63360, "inches")
            print (amount * 5280, "feet")
            print (amount * 1760, "yards")
            print ("\n")

            cont = 0
            while cont == 0:
                again = input("Do you want to restart? Yes or No ")
                again = again.lower()
                if again == "yes":
                    cont = 1
                    again = 0
                if again == "no":
                    cont = 1
                    print ("Goodbye")
            print ("\n")