/* -*- coding: utf-8 -*-
 *
 * 1389.cc:  No.1389 Clumsy Calculation - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int ss[MAX_N];

/* subroutines */

/* main */

int main() {
  int n, x;
  scanf("%d%d", &n, &x);

  ll ssum = 0;
  for (int i = 0; i < n; i++) scanf("%d", ss + i), ssum += ss[i];

  ll ai = (ll)n * x - ssum;
  printf("%lld\n", x - ai);
  return 0;
}