while True:
    try:
        num1 = int(input('Enter a number for variable one: '))
        num2 = int(input('Enter a number for variable two: '))
        num3 = int(input('Enter a number for variable three: '))
        break
    except ValueError:
        print('Re-enter the numbers. ')
l = [num1, num2, num3]
print(l)
l = sorted(l)
print(l)
print(l[-1])