[백준-BOJ] 3046

www.acmicpc.net/problem/3046

3046번: R2

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;
 
public class Main {
    public static void main(String[] args) throws IOException {
        Main m = new Main();
        m.doit();
    }
     
     
     
    public void doit() throws IOException{
       // System.setIn(new FileInputStream("input.txt"));
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        
        String [] input = br.readLine().split(" ");
        int ret = 2 * (Integer.parseInt(input[1])) - Integer.parseInt(input[0]);
        System.out.println(ret);
        br.close();
    }
}