#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,m;
    int sum = 0;
    int tmp;
    cin>>n>>m;
    for(int i=0; i<n; i++)
    {
        cin>>tmp;
        sum+=tmp;
    }
    cout<<(sum-m*(n-1))<<endl;
}