Everyone is familiar to the natural number system: 1, 2, 3… Today we will consider a different one: a no-zero number system, which means it only uses the digits 1 through 9. So counting begins with 1, the first "counting number", and continues: 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12…, 19, 21…, 98, 99, 111, 112…
So, in this system 9 is the ninth counting number and 11 is the tenth counting number. As usual, addition can be defined by reference to the counting sequence. Addition of the i-th counting number and the j-th counting number is defined to mean the (i+j)-th counting number. Thus, in this system 5 + 8 = 14, since 5 is the fifth counting number, 8 is the eighth, and 14 is the thirteenth counting number. Subtraction is the reverse of addition.
Here is your task, given two numbers: a and b, you should output a subtract b which is defined in no-zero number system.