#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<stack>
#include<queue>
#include<vector>
#include<algorithm>
#include<string>
#include<iostream>
typedef long long ll;
using namespace std;
int min4(int a,int b,int c,int d){
    if(a<b)b=a;
    if(b<c)c=b;
    if(c<d)d=c;
    return d;
}
int min3(int a,int b,int c){
    if(a<b)b=a;
    if(b<c)c=b;
    return c;
}


int main(){
    int n,p;cin>>n>>p;
    int a[n+1],b[n+1],c[n+1];for(int i=1;i<=n;i++)cin>>a[i]>>b[i]>>c[i];
    int dp[n+1][p+1];
    for(int j=0;j<=p;j++)dp[0][j]=0;
    for(int i=1;i<=n;i++)for(int j=0;j<=p;j++){
        if(j==0)dp[i][j]=dp[i-1][j]+a[i];
        else if(j==1)dp[i][j]=min(dp[i-1][j]+a[i],dp[i-1][j-1]+b[i]);
        else if(j==2)dp[i][j]=min3(dp[i-1][j]+a[i],dp[i-1][j-1]+b[i],dp[i-1][j-2]+c[i]);
        else dp[i][j]=min4(dp[i-1][j]+a[i],dp[i-1][j-1]+b[i],dp[i-1][j-2]+c[i],dp[i-1][j-3]+1);
    }
    cout<<(double)dp[n][p]/n<<endl;
    
    
    return 0;
}