Decrement OR Increment

Problem statement

A warehouse uses a simple parity rule to move an inventory marker to a neighboring numbered slot. A marker in an even-numbered slot moves one slot backward, while a marker in an odd-numbered slot moves one slot forward. The operator needs a program that reports the destination after this single adjustment. Your task Given an integer N, output N - 1 if N is even, or N + 1 if N is odd. Perform exactly one adjustment. Important details There is only one number in the input, not a test-case count. Determine parity from the original number. Do not apply the rule again to the destination, since the machine makes only one move. Worked example A marker at slot 8 moves backward to slot 7 because 8 is even. A marker at slot 9 moves forward to slot 10 because 9 is odd.

Input format

One line contains the integer N.

Output format

Print the resulting integer.

Constraints

0 <= N <= 1000000000.

Sample input

8

Sample output

7