N,V=map(int,raw_input().split())
C=map(int,raw_input().split())
s=0
S=[]
A=[]
for i in range(N):
    s+=C[i]
    S.append(s)
    A.append((s/(1.0+i),i))
A.sort()

i=0
v=N
p=s
while v < V:
    while A[i][1]+1 > V-v:
        i+=1
    t = (V-v)/(A[i][1]+1)
    v+= t*(A[i][1]+1)
    p+= t*S[A[i][1]]
print p