import sys
stdin=sys.stdin

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

n,p=lp()
inf=float('inf')
dp=[inf for _ in range(p+1)]
dp[0]=0
for _ in range(n):
    now=lp()
    for i in  range(p,-1,-1):
        dp[i]+=now[0]
        if i-1>=0:
            dp[i]=min(dp[i-1]+now[1],dp[i])
        if i-2>=0:
            dp[i]=min(dp[i-2]+now[2],dp[i])
        if i-3>=0:
            dp[i]=min(dp[i-3]+now[3],dp[i])
print(dp[-1]/n)