count frequency 
      0 514 
      1 503 
      2 457 
      3 423 
      4 326 
      5 233 
      6 195 
      7 139 
      8 101 
      9 77 
      10 56 
      11 40 
      12 37 
      13 22 
      14 9 
      15 7 
      16 10 
      17 9 
      18 3 
      19 2 
      20 2 
      21 2 
      22 0 
      23 0 
      24 0 
      25 0 
      26 0 
      27 0 
      28 0 
      29 0 
      30 1