import java.util.*; import java.io.*; public class Main { public static void main(String[] args) { FastScanner sc = new FastScanner(); int n = sc.nextInt(); int p = sc.nextInt(); long[] a = new long[n]; long[] b = new long[n]; long[] c = new long[n]; for (int i = 0; i < n; i++) { a[i] = sc.nextLong(); b[i] = sc.nextLong(); c[i] = sc.nextLong(); } long[][] dp = new long[n + 1][p + 1]; dp[0][0] = 0; for (int i = 1; i <= n; i++) { for (int j = 0; j <= p; j++) { dp[i][j] = dp[i - 1][j] + a[i - 1]; if (j - 1 >= 0) { dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 1] + b[i - 1]); } if (j - 2 >= 0) { dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 2] + c[i - 1]); } if (j - 3 >= 0) { dp[i][j] = Math.min(dp[i][j], dp[i - 1][j - 3] + 1); } } } // System.out.println(Arrays.deepToString(dp)); float ans = dp[n][p] / (float) n; System.out.printf("%.5f%n", ans); } } class FastScanner { private final InputStream in = System.in; private final byte[] buffer = new byte[1024]; private int ptr = 0; private int buflen = 0; private boolean hasNextByte() { if (ptr < buflen) { return true; } else { ptr = 0; try { buflen = in.read(buffer); } catch (IOException e) { e.printStackTrace(); } if (buflen <= 0) { return false; } } return true; } private int readByte() { if (hasNextByte()) return buffer[ptr++]; else return -1; } private static boolean isPrintableChar(int c) { return 33 <= c && c <= 126; } public boolean hasNext() { while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++; return hasNextByte(); } public String next() { if (!hasNext()) throw new NoSuchElementException(); StringBuilder sb = new StringBuilder(); int b = readByte(); while (isPrintableChar(b)) { sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } public long nextLong() { if (!hasNext()) throw new NoSuchElementException(); long n = 0; boolean minus = false; int b = readByte(); if (b == '-') { minus = true; b = readByte(); } if (b < '0' || '9' < b) { throw new NumberFormatException(); } while (true) { if ('0' <= b && b <= '9') { n *= 10; n += b - '0'; } else if (b == -1 || !isPrintableChar(b)) { return minus ? -n : n; } else { throw new NumberFormatException(); } b = readByte(); } } public int nextInt() { long nl = nextLong(); if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) throw new NumberFormatException(); return (int) nl; } public double nextDouble() { return Double.parseDouble(next()); } }