import sys
sys.setrecursionlimit(10**6)
inf=float('inf')

N,P=map(int,input().split())
A,B,C=[0]*N,[0]*N,[0]*N

for i in range(N):
    A[i],B[i],C[i]=map(int,input().split())

dp=[[inf]*(P+1) for i in range(N+1)]
dp[0][0]=0

for i in range(N):
    for j in range(P+1):
        dp[i+1][j]=dp[i][j]+A[i]
        if 1<=j:
            dp[i+1][j]=min(dp[i+1][j],dp[i][j-1]+B[i])
        if 2<=j:
            dp[i+1][j]=min(dp[i+1][j],dp[i][j-2]+C[i])
        if 3<=j:
            dp[i+1][j]=min(dp[i+1][j],dp[i][j-3]+1)
print(dp[N][P]/N)