title: How to add alphabet in starting numbers of rows?
body: <p>i have a PDB file like this :</p>
  
  <pre><code>ATOM    954  N   ASP     1      97.850  62.880  40.170  1.00  0.00            
  ATOM    955  H1  ASP     1      98.220  63.100  39.260  1.00  0.00            
  ATOM    956  H2  ASP     1      97.790  63.720  40.710  1.00  0.00            
  ATOM    957  H3  ASP     1      98.460  62.200  40.580  1.00  0.00            
  ATOM    958  CA  ASP     1      96.560  62.200  40.040  1.00  0.00            
  ATOM    959  CB  ASP     1      95.890  62.050  41.400  1.00  0.00            
  ATOM    960  CG  ASP     1      96.590  60.930  42.180  1.00  0.00            
  ATOM    961  OD1 ASP     1      97.470  61.280  42.990  1.00  0.00            
  ATOM    962  OD2 ASP     1      96.160  59.770  42.060  1.00  0.00            
  ATOM    963  C   ASP     1      95.660  62.960  39.060  1.00  0.00            
  ATOM    964  O   ASP     1      95.660  64.190  39.190  1.00  0.00            
  ATOM    965  N   VAL     2      94.670  62.290  38.480  1.00  0.00            
  ATOM    966  H   VAL     2      94.490  61.350  38.770  1.00  0.00
  ATOM    967  CA  VAL     2      93.820  62.870  37.430  1.00  0.00            
  ATOM    968  CB  VAL     2      93.500  61.690  36.500  1.00  0.00            
  ATOM    969  CG1 VAL     2      92.540  62.050  35.360  1.00  0.00            
  ATOM    970  CG2 VAL     2      94.710  60.950  35.930  1.00  0.00            
  ATOM    971  C   VAL     2      92.540  63.390  38.080  1.00  0.00            
  ATOM    972  O   VAL     2      91.980  62.790  39.000  1.00  0.00            
  ATOM    973  N   GLN     3      92.410  64.690  37.830  1.00  0.00            
  ATOM    974  H   GLN     3      93.140  65.240  37.410  1.00  0.00            
  ATOM    975  CA  GLN     3      91.290  65.510  38.310  1.00  0.00                    
  </code></pre>
  
  <p>in column 4 (code of amino acid) i want to add alphabet "H" till 972 atom number . can any one kinldy explain me how i can do this.</p>
  
  <p>expected outcome:</p>
  
  <pre><code>ATOM    954  N   ASP H    1      97.850  62.880  40.170  1.00  0.00            
  ATOM    955  H1  ASP H   1      98.220  63.100  39.260  1.00  0.00            
  ATOM    956  H2  ASP H   1      97.790  63.720  40.710  1.00  0.00            
  ATOM    957  H3  ASP H   1      98.460  62.200  40.580  1.00  0.00            
  ATOM    958  CA  ASP H   1      96.560  62.200  40.040  1.00  0.00            
  ATOM    959  CB  ASP H   1      95.890  62.050  41.400  1.00  0.00            
  ATOM    960  CG  ASP H   1      96.590  60.930  42.180  1.00  0.00            
  ATOM    961  OD1 ASP H    1      97.470  61.280  42.990  1.00  0.00            
  ATOM    962  OD2 ASP H    1      96.160  59.770  42.060  1.00  0.00            
  ATOM    963  C   ASP H    1      95.660  62.960  39.060  1.00  0.00            
  ATOM    964  O   ASP H    1      95.660  64.190  39.190  1.00  0.00            
  ATOM    965  N   VAL H    2      94.670  62.290  38.480  1.00  0.00            
  ATOM    966  H   VAL H    2      94.490  61.350  38.770  1.00  0.00
  ATOM    967  CA  VAL H    2      93.820  62.870  37.430  1.00  0.00            
  ATOM    968  CB  VAL H    2      93.500  61.690  36.500  1.00  0.00            
  ATOM    969  CG1 VAL H   2      92.540  62.050  35.360  1.00  0.00            
  ATOM    970  CG2 VAL H   2      94.710  60.950  35.930  1.00  0.00            
  ATOM    971  C   VAL H    2      92.540  63.390  38.080  1.00  0.00            
  ATOM    972  O   VAL H   2      91.980  62.790  39.000  1.00  0.00 
  </code></pre>