import sys
input = sys.stdin.readline

N,P=map(int,input().split())

DP=[1<<30]*(P+1)
DP[0]=0

for i in range(N):
    a,b,c=map(int,input().split())
    NDP=[1<<30]*(P+1)

    for j in range(P+1):
        if DP[j]>=(1<<30):
            continue

        if j<=P:
            NDP[j]=min(NDP[j],DP[j]+a)

        if j+1<=P:
            NDP[j+1]=min(NDP[j+1],DP[j]+b)

        if j+2<=P:
            NDP[j+2]=min(NDP[j+2],DP[j]+c)

        if j+3<=P:
            NDP[j+3]=min(NDP[j+3],DP[j]+1)
    DP=NDP
        
print(DP[P]/N)