import sys
input = lambda : sys.stdin.readline().rstrip()

sys.setrecursionlimit(2*10**5+10)
write = lambda x: sys.stdout.write(x+"\n")

n,x = list(map(int, input().split()))
s = list(map(int, input().split()))
ss = sum(s)
ak = n*x - ss
ans = x - ak
print(ans)