#include <cstdio>
#include <algorithm>
using namespace std;
#define REP(i,n) for(int i=0;i<(int)(n);++i)

#define CHMIN(a,b) a=min((a),(b))
#define CHMAX(a,b) a=max((a),(b))

int dp[2][15252];
int vs[5252][4];

const int INF = 1<<30;

int main(){
  int n,p;
  scanf("%d%d",&n,&p);
  REP(i,n)scanf("%d%d%d",vs[i]+0,vs[i]+1,vs[i]+2);
  fill(dp[0],dp[0]+p+1,INF);
  int cur = 0;
  dp[cur][0] = 0;
  REP(i,n){
    vs[i][3] = 1;
    fill(dp[cur^1],dp[cur^1]+p+1,INF);
    REP(j,p+1){
      CHMIN(dp[cur^1][j+0],dp[cur][j]+vs[i][0]);
      CHMIN(dp[cur^1][j+1],dp[cur][j]+vs[i][1]);
      CHMIN(dp[cur^1][j+2],dp[cur][j]+vs[i][2]);
      CHMIN(dp[cur^1][j+3],dp[cur][j]+vs[i][3]);
    }
    cur ^= 1;
  }
  printf("%.10f\n",(double)dp[cur][p] / n);
  return 0;
}