const
  VELOCITY = 10;

var
  N, K, i, j: integer;
  f1, f2: text;
  a: Array [0..11, 0..10001] of integer;
  b: Array [0..11, 0..10001] of double;
  minValue: double;

begin
  assign(f1, 'input.txt');
  reset(f1);
  assign(f2, 'output.txt');
  rewrite(f2);
  read(f1, N, K);
  readln(f1);
  for i:=0 to 11 do
    for j:=0 to 10001 do
      b[i,j]:=10*10000;
  i:=0;
  try
  while (Not Eof(f1)) do
  begin
    i+=1;
    j:=0;
    while (Not Eoln(f1)) do
    begin
      j+=1;
      read(f1,a[i,j]);
    end;
    readln(f1);
  end;
  except
    exit;
  end;


  for i := 1 to N do
  begin
    b[i, 1] := VELOCITY / a[i, 1];
  end;


  for i := 2 to K do
  begin
    for j := 1 to N do
    begin
      b[j, i] := VELOCITY / a[j, i] + b[j, i - 1];
      if (j - 1) > 0 then
        b[j, i] := min(b[j, i], VELOCITY / a[j, i] + b[j - 1, i - 1]);
      if (j + 1) <= N then
        b[j, i] := min(b[j, i], VELOCITY / a[j, i] + b[j + 1, i - 1]);
    end;
  end;

  minValue := b[1, k];
  for j := 2 to n do
    if (b[j, k] < minValue) then
      minValue := b[j, k];
  write(f2, minValue:0:3);
  close(f1);
  close(f2);
end.