import java.util.*;
import java.io.*;

public class Main {
	static IO io = new IO();
	public static void main(String[] args) {
		int r = io.nextInt();
		int g = io.nextInt();
		System.out.println(2*g-r);
	}
	
	static class IO extends PrintWriter {
		private final InputStream in;
		private final byte[] buffer = new byte[1024];
		private int ptr = 0;
		private int buflen = 0;

		public IO() { this(System.in);}
		public IO(InputStream source) { super(System.out); this.in = source;}
		private boolean hasNextByte() {
			if (ptr < buflen) {
				return true;
			}else{
				ptr = 0;
				try {
					buflen = in.read(buffer);
				} catch (IOException e) {
					e.printStackTrace();
				}
				if (buflen <= 0) {
					return false;
				}
			}
			return true;
		}
		private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1;}
		private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126;}
		private static boolean isNewLine(int c) { return c == '\n' || c == '\r';}
		private void skipUnprintable() { while(hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;}
		private void skipNewLine() { while(hasNextByte() && isNewLine(buffer[ptr])) ptr++;}
		public boolean hasNext() { skipUnprintable(); return hasNextByte();}
		public boolean hasNextLine() { skipNewLine(); return hasNextByte();}
		public String next() {
			if (!hasNext()) {
				throw new NoSuchElementException();
			}
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while(isPrintableChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
		public char[] nextCharArray(int len) {
			if (!hasNext()) {
				throw new NoSuchElementException();
			}
			char[] s = new char[len];
			int i = 0;
			int b = readByte();
			while(isPrintableChar(b)) {
				if (i == len) {
					throw new InputMismatchException();
				}
				s[i++] = (char) b;
				b = readByte();
			}
			return s;
		}
		public String nextLine() {
			if (!hasNextLine()) {
				throw new NoSuchElementException();
			}
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while(!isNewLine(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
		public long nextLong() {
			if (!hasNext()) {
				throw new NoSuchElementException();
			}
			long n = 0;
			boolean minus = false;
			int b = readByte();
			if (b == '-') {
				minus = true;
				b = readByte();
			}
			if (b < '0' || '9' < b) {
				throw new NumberFormatException();
			}
			while(true){
				if ('0' <= b && b <= '9') {
					n *= 10;
					n += b - '0';
				}else if(b == -1 || !isPrintableChar(b)){
					return minus ? -n : n;
				}else{
					throw new NumberFormatException();
				}
				b = readByte();
			}
		}
		public int nextInt() {
			long nl = nextLong();
			if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
				throw new NumberFormatException();
			}
			return (int) nl;
		}
		public char nextChar() {
			if (!hasNext()) {
				throw new NoSuchElementException();
			}
			return (char) readByte();
		}
		public double nextDouble() { return Double.parseDouble(next());}
		public int[] arrayInt(int n) { int[] a = new int[n]; for(int i=0;i<n;i++) a[i] = nextInt(); return a;}
		public long[] arrayLong(int n) { long[] a = new long[n]; for(int i=0;i<n;i++) a[i] = nextLong(); return a;}
		public double[] arrayDouble(int n) { double[] a = new double[n]; for(int i=0;i<n;i++) a[i] = nextDouble(); return a;}
		public void arrayInt(int[]... a) {for(int i=0;i<a[0].length;i++) for(int j=0;j<a.length;j++) a[j][i] = nextInt();}
		public int[][] matrixInt(int n,int m) { int[][] a = new int[n][]; for(int i=0;i<n;i++) a[i] = arrayInt(m); return a;}
		public char[][] charMap(int n,int m) { char[][] a = new char[n][]; for(int i=0;i<n;i++) a[i] = nextCharArray(m); return a;}
		public void close() {
			super.close();
			try {
				in.close();
			} catch (IOException e) {}
		}
	}
}


Measured memory_bytes: 22484