백준 3046 java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.Buffer;
import java.util.StringTokenizer;

public class bj3046 {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine(), " ");
        int R1, avg, R2;

        R1 = Integer.parseInt(st.nextToken());
        avg = Integer.parseInt(st.nextToken());
        R2 = 2*avg - R1;

        System.out.println(R2);
        //System.out.println(R1);
        //System.out.println(avg);
    }
}