#include <cstdio>
#include <algorithm>
using namespace std;

int a[200005]={};

int main()
{
    int n,s;
    scanf("%d %d",&n,&s);
    for(int i=0; i<n; i++)
    {
        scanf("%d",&a[i]);
    }  
    sort(a,a+n);
    long long np=s;
    int li=0;    
    int ri=n-1;  
    for(int k=0; k<n; k++)
    {
        if(n%2==0)
        {
            if(k%2==0)
            {
                np=2*a[li]-np;
                li++;
            }
            else           
            {
                np=2*a[ri]-np;
                ri--;
            }
        }
        else
        {
            if(k%2==0)
            {
                np=2*a[ri]-np;
                ri--;
            }
            else
            {
                np=2*a[li]-np;
                li++;
            }
        }
    }
    
    printf("%lld",np);
    return 0;
}