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# P4413 [COCI2006-2007#2] R2

P4413 [COCI2006-2007#2] R2

## 题目描述

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.

## 输入格式

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

## 输出格式

Output R2 on a single line.

## 题意翻译

S=(R1+R2)/2，给定R1与S (-1000<=R1,S<=1000)(−1000<=R1,S<=1000)，求R2。

## 输入输出样例

11 15

19

4 3

2

#include<bits/stdc++.h>

using namespace std;

int x=0,f=0;char c=getchar();

while(!isdigit(c)){if(c=='-')f=1;c=getchar();}

while(isdigit(c)){

x=x*10+c-'0';

c=getchar();

}

return f?-x:x;

}

int r1,s;

void init(){

}

void get_ans(){

cout<<s*2-r1;

}

int main(){

init();get_ans();

return 0;

}

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