n, x = map(int, input().split())
S = list(map(int, input().split()))
A = [0]*n
B = [0]*n
for i, s in enumerate(S):
    A[i] = x-s
    B[i] = x-s//2
y = sum(A)
for i in range(n):
    if y-A[i]+B[i] == x:
        print(x-B[i])
        exit()