#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define rep(i,a,b) for(i=a;i<b;i++)

int cha(const void*a,const void*b){
  if(*(int*)a >*(int*)b){
    return 1;
  }else if(*(int*)a <*(int*)b){
    return -1;
  }else{
    return 0;
  }
}


int main(void){
    int d,i,j,kk=0,ma,mb,p;
  int mini=1000,k=0,qi=0,qj=0,n;
  int s=0,h=0;
  int a[5010],b[5010],c[5010],w=0;
  int heavy=1e9;
  int x_size = 3;  // 1次元のサイズ
  int y_size = 5010;  // 2次元のサイズ
  int z_size = 5010;  // 3次元のサイズ

  // 三次元配列の動的確保
  int ***dp;

  dp = (int ***)malloc(x_size * sizeof(int**));
  for (int i = 0; i < x_size; ++i) {
      dp[i] = (int **)malloc(y_size * sizeof(int*));
      for (int j = 0; j < y_size; ++j) {
          dp[i][j] = (int *)malloc(z_size * sizeof(int));
      }
  }
  scanf("%d%d",&n,&p);
 rep(i,1,n+1){
   scanf("%d%d%d",&a[i],&b[i],&c[i]);
 }
  rep(i,0,n+1){
    rep(j,0,15000){
      dp[0][i][j]=heavy;
    }
  }
  rep(i,0,4){
    dp[0][0][i]=0;
  }
  rep(i,1,n+1){
    rep(j,0,i*3+1){
      if(j==0){
        dp[0][i][0]=dp[0][i-1][0]+a[i];
      }
      if(j==1){
        dp[0][i][1]=fmin(dp[0][i-1][1]+a[i],dp[0][i-1][0]+b[i]);
      }
      if(j==2){
        dp[0][i][2]=fmin(dp[0][i-1][0]+c[i],dp[0][i-1][1]+b[i]);
        dp[0][i][2]=fmin(dp[0][i][2],dp[0][i-1][2]+a[i]);
      }
      if(j==3){
        dp[0][i][3]=fmin(dp[0][i-1][0]+1,dp[0][i-1][1]+c[i]);
        dp[0][i][3]=fmin(dp[0][i][3],dp[0][i-1][2]+b[i]);
        dp[0][i][3]=fmin(dp[0][i][3],dp[0][i-1][3]+a[i]);
      }
      if(j>=4){
      dp[0][i][j]=fmin(dp[0][i-1][j-1]+b[i],dp[0][i-1][j-2]+c[i]);
       dp[0][i][j]=fmin(dp[0][i][j],dp[0][i-1][j-3]+1);
        dp[0][i][j]=fmin(dp[0][i][j],dp[0][i-1][j]+a[i]);
      }
    }
    }
    double sss=0.0;
    sss=(double)dp[0][n][p]/n;
    printf("%lf\n",sss);
    
  
  free(dp);
  }