import sys
stdin=sys.stdin

ip=lambda: int(sp())
fp=lambda: float(sp())
lp=lambda:list(map(int,stdin.readline().split()))
sp=lambda:stdin.readline().rstrip()
yp=lambda:print('Yes')
np=lambda:print('No')

n,p=lp()
a=[]
for _ in range(n):
    now=lp()
    now.append(1)
    a.append(now)

inf=float('INF')
dp=[[inf for _ in range(3*n+1)]for _ in range(n)]
dp[0][0]=a[0][0]
dp[0][1]=a[0][1]
dp[0][2]=a[0][2]
dp[0][3]=a[0][3]

for i in range(1,n):
    for j in range(3*n+1):
        dp[i][j]=min(dp[i][j],dp[i-1][j]+a[i][0])
        if 0<=j-1:
            dp[i][j]=min(dp[i][j],dp[i-1][j-1]+a[i][1])
        if 0<=j-2:
            dp[i][j]=min(dp[i][j],dp[i-1][j-2]+a[i][2])
        if 0<=j-3:
            dp[i][j]=min(dp[i][j],dp[i-1][j-3]+a[i][3])

print(dp[-1][p]/n)