import java.io.*; import java.util.*; import java.math.*; // import java.awt.Point; public class Main { InputStream is; PrintWriter out; String INPUT = ""; long MOD = 1_000_000_007; long inf = Long.MAX_VALUE; void solve() { int n = ni(); int p = ni(); int[][] a = new int[n][4]; for(int i = 0; i < n; i++){ a[i][0] = ni(); a[i][1] = ni(); a[i][2] = ni(); a[i][3] = 1; } long[] dp = new long[3*n+2]; Arrays.fill(dp,inf/2); dp[0] = 0; long[] ndp = new long[3*n+2]; for(int i = 0; i < n; i++){ for(int j = 0; j <= 3*(i+1); j++){ long res1 = Math.min(dp[j]+a[i][0], j>0?dp[j-1]+a[i][1]:inf); long res2 = Math.min(j>1?dp[j-2]+a[i][2]:inf, j>2?dp[j-3]+a[i][3]:inf); ndp[j] = Math.min(res1,res2); } // out.println(ndp[3*(i+1)]); for(int j = 0; j <= 3*(i+1); j++){ dp[j] = ndp[j]; ndp[j] = 0; } } out.println((double)dp[p]/n); } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); } public static void main(String[] args) throws Exception { new Main().run(); } private byte[] inbuf = new byte[1024]; private int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b) && b != ' ')){ sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private int ni() { int num = 0, b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }