MathWorlds
At the last moment, the olympiad organizers decided to replace one of the problems. The new problem is based on the game MathWorlds, where the player is given a formula in the form "x [operator] y = z". The player must select one of the operators "+" (addition), "-" (subtraction), "*" (multiplication), or "/" (division) to make the formula correct. Zebra Hippo, who is responsible for coordinating the problem preparation, has asked you to write a program that checks the validity of the formulas generated for the game.
You are provided with three integers x, y, and z. Your task is to output the operator that, when placed in the expression "x [operator] y = z", makes the formula true. If no such operator exists or if more than one operator can make the formula true, output "Invalid". Note that division ("/") in this context is exact, not integer.
Input
The input file contains three integers x, y, and z (0 ≤ x, y, z ≤ 10^9), separated by spaces.
Output
Output one of the following lines based on the result of the evaluation: "+", "-", "*", "/" or "Invalid".