java 6749

import java.io.BufferedReader;
import java.io.InputStreamReader;

class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        int third = Integer.parseInt(br.readLine());
        int second = Integer.parseInt(br.readLine());

        int Difference = second - third;
        int first = second + Difference;

        System.out.println(first);

    }
}