import java.util.*;
public class candyfactory_xiaowuc1 {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int k = sc.nextInt();
    long[] v = new long[n];
    for(int i = 0; i < n; i++) v[i] = sc.nextInt();
    long lhs = 1;
    long rhs = (long)(1e18 / k);
    while(lhs < rhs) {
      long mid = (lhs+rhs)/2;
      long max = 0;
      long sum = 0;
      for(int i = 0; i < n; i++) {
        max = Math.max(max, v[i]);
        sum += v[i];
      }
      if(k*mid < sum || mid < max) lhs = mid+1;
      else rhs = mid;
    }
    long ret = lhs * k;
    for(long out: v) ret -= out;
    System.out.println(ret);
  }
}