[summer daily question] Luogu p4413 [coci2006-2007 2] R2

Topic link ：P4413 [COCI2006-2007#2] R2 - Luogu | New ecology of computer science education (luogu.com.cn)

Topic translation

set up S=(R1+R2)/2, Given R1 And S (-1000<=R1,S<=1000), seek R2.

thank @Xeonacid Translation provided

Title Description

The number S is called the mean of two numbers R1 and R2 if S is equal to (R1+R2)/2. Mirko's birthday present for Slavko was two integers R1 and R2. Slavko promptly calculated their mean which also happened to be an integer but then lost R2! Help Slavko restore R2.

Input format

The first and only line of input contains two integers R1 and S, both between -1000 and 1000.

Output format

Output R2 on a single line.

Examples #1

The sample input #1

11 15

Sample output #1

19

Examples #2

The sample input #2

4 3

Sample output #2

2

AC code: 

#include<iostream>
#include<algorithm>

using namespace std;

int main()
{
	int r1,s;
	cin>>r1>>s;
	cout<<2*s-r1;
	
	return 0;
}