HDU 5066 Harry And Physical Teacher(数学)

#include<iostream>
#include<cstdio>
#include<set>
#include<string>
#include<string.h>
#include<cstring>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<cctype>
#include<algorithm>
#include<sstream>
#include<utility>
#include<cmath>
#include<functional>
#define mt(a) memset(a,0,sizeof (a))
#define fl(a,b,c) fill(a,b,c)
#define SWAP(a,b,t) (t=a,a=b,b=t)

#define inf 1000000000+7

using namespace std;
typedef long long ll;

int main()
{
ll x, y;
while (cin >> x >> y)
{
cout <<2*x-y << endl;
}
return 0;
}