N, P = map(int, input().split())
abc = [tuple(map(int, input().split())) for _ in range(N)]
dp = [[10**18]*(P+1) for _ in range(N+1)]
dp[0][0] = 0

for i in range(N):
    ai, bi, ci = abc[i]
    
    for j in range(P+1):
        dp[i+1][j] = min(dp[i+1][j], dp[i][j]+ai)
        
        if j+1<=P:
            dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j]+bi)
        
        if j+2<=P:
            dp[i+1][j+2] = min(dp[i+1][j+2], dp[i][j]+ci)
        
        if j+3<=P:
            dp[i+1][j+3] = min(dp[i+1][j+3], dp[i][j]+1)

print(dp[N][P]/N)