#!/usr/bin/python3
import sys

n, k = [int(v) for v in sys.stdin.readline().split(' ')]
sum = 0
maxq = 0
for _ in range(n):
  q = int(sys.stdin.readline())
  sum += q
  maxq = max(maxq, q)
print (max(k * maxq, (sum + k - 1) // k * k) - sum)