n,k=list(map(int,input().split()))
a=list()
for i in range(n):
x=float(input())*100
a.append(int(x))
def check(x):
cnt=0
for i in a:
cnt=cnt+i//x
return cnt>=k
l=0
r=sum(a)//n
mid=0
ans=0
while l<=r:
mid=(l+r)//2
if check(mid):
ans=mid
l=mid+1
else:
r=mid-1
ans=ans/100
print('%.2f'%ans)
