import math
print("The format you should consider:")
print str("value 1a")+str(" + ")+str("value 2")+str(" = ")+str("value 3a ")+str("value 4")+str("\n")
print("Do not include the letters in the input, it automatically adds them")
v1 = input("Value 1: ")
v2 = input("Value 2: ")
v3 = input("Value 3: ")
v4 = input("Value 4: ")
lista = [v1, v3]
lista = list.sort(lista)
a = lista[1] - lista[0]
list = [v2, v4]
list = list.sort(list)
b = list[1] = list[0]
print str(a)+str("a")+str(" = ")+str(b)
check this code.
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