#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 n,p;
int a[5252],b[5252],c[5252];
int dp[2][15252];

const int INF = 1<<30;

int main(){
  scanf("%d%d",&n,&p);
  fill(dp[0],dp[0]+3*n+1,INF);
  int cur = 0;
  dp[cur][0] = 0;
  REP(i,n){
    int vs[4] = {0,0,0,1};
    scanf("%d%d%d",vs+0,vs+1,vs+2);
    fill(dp[cur^1],dp[cur^1]+3*n+1,INF);
    REP(k,4)REP(j,3*n+1){
      CHMIN(dp[cur^1][j+k],dp[cur][j]+vs[k]);
    }
    cur ^= 1;
  }
  printf("%.10f\n",(double)dp[cur][p] / n);
  return 0;
}