Problem:
Score: 100 points

Problem Statement

We have two distinct integers A and B.

Print the integer K such that |A - K| = |B - K|.

If such an integer does not exist, print IMPOSSIBLE instead.

Constraints

All values in input are integers.

0 \leq A,\ B \leq 10^9

A and B are distinct.

Input

Input is given from Standard Input in the following format:

A B

Output

Print the integer K satisfying the condition.

If such an integer does not exist, print IMPOSSIBLE instead.

Sample Input 1

2 16

Sample Output 1

9

|2 - 9| = 7 and |16 - 9| = 7, so 9 satisfies the condition.

Sample Input 2

0 3

Sample Output 2

IMPOSSIBLE

No integer satisfies the condition.

Sample Input 3

998244353 99824435

Sample Output 3

549034394

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;


public class Main {
    
    public static void main(String[] args) {
        
        Scanner  input = new Scanner(System.in);
        
        int A = input.nextInt();
        int B = input.nextInt();
        
        int count = 0; int i ;
        if(A>B){
        
            for ( i = 0; i >= 0; i++) {
                int x= Math.abs(A - i);
                int y = Math.abs(B - i);
                Math.abs(x);
                Math.abs(y);
                System.out.println(x+" "+y);
                if (x == y){
                count ++;
                break;
                }
            }
            if (count > 0 ){
            System.out.println(i); }
            else{
                System.out.println("IMPOSSIBLE");
            }
        }
    }
}