#include<stdio.h>
#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)<(b)?(a):(b))
long dp[2][15001];
long a[5000],b[5000],c[5000];
int main(){
	int i,n,p,j;
	scanf("%d %d",&n,&p);
	for(i=0;i<n;i++){
		scanf("%ld %ld %ld",&a[i],&b[i],&c[i]);
	}
	dp[0][0]=a[0];
	dp[0][1]=b[0];
	dp[0][2]=c[0];
	dp[0][3]=1;
	for(i=1;i<n;i++){
		for(j=max(0,p-(n-i)*3);j<=p;j++){
			dp[i%2][j]=dp[(i+1)%2][j]+a[i];
			if(j==0) continue;
			dp[i%2][j]=min(dp[i%2][j],dp[(i+1)%2][j-1]+b[i]);
			if(j==1) continue;
			dp[i%2][j]=min(dp[i%2][j],dp[(i+1)%2][j-2]+c[i]);
			if(j==2) continue;
			dp[i%2][j]=min(dp[i%2][j],dp[(i+1)%2][j-3]+1);
		}
	}
	printf("%f\n",(double)dp[(n+1)%2][p]/(double)n);
	return 0;
}