Minimum Moves to Equal Candy Bars

There are candies of three different flavors, with counts A, B, and C. Each operation picks two candies of different flavors and turns both into the third flavor, so the two chosen counts each decrease by 1 and the third increases by 2, keeping the total unchanged. Only flavors that currently have candies can be chosen. Find the minimum number of operations to make all candies the same flavor; if impossible, output −1. The goal is for two flavor counts to be 0, not for all three counts to be equal.

输入格式

One line with three integers A, B, C, 1≤A,B,C≤100000000. Initially all three flavors have candies, and a count may become 0 during the process. The fixed original problem's ranges are kept in full.

输出格式

Output the minimum number of operations; if unreachable, output -1.

样例 1

输入：

1 2 3

输出：

-1

样例 2

输入：

1 1 1

输出：

1

样例 3

输入：

4 1 2

输出：

4

样例说明

Example 1 comes from the fixed original problem: (1,2,3) cannot become a single flavor. Examples 2 and 3 are added by this site: (1,1,1) becomes (0,0,3) in one step; (4,1,2) can become (3,3,1), (2,2,3), (1,1,5), (0,0,7) in turn, for a minimum of 4 steps. The original compiled version additionally required the sum of the counts to be cleared to be divisible by 3, which is a wrong condition; this site solves the original operations independently.