[modeller_usage] No atoms were read form the specified input pdb file

Dear All, While running the model-single.py, I am getting the following error--- No atoms were read form the specified input pdb file since the starting residue no and/ or chain ID in Model_Segment <or the alignment file header> was not found; requested starting position residue no "0" chain "A" My model file starts with residue no 4. Please help. Thanks J