update readme

README.md

@@ -39,7 +39,7 @@ If you use `DataBack` in your research, please kindly cite [our paper](https://a
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 ## File Naming Convention
-In the original directory, each CNF tar file contains compressed CNF files named: `[cnf_name].cnf.[compression_format]`, where `[compression_format]` could be bz2, lzma, xz, gz, etc. Correspondingly, each backbone tar file comprises compressed backbone files named: `[cnf_name].cnf.backbone.xz`. It is important to note that a compressed CNF file will always share its `[cnf_name]` with its associated compressed backbone file.
+In the original directory, each CNF tar file contains compressed CNF files named: `[cnf_name].[compression_format]`, where `[compression_format]` could be bz2, lzma, xz, gz, etc. Correspondingly, each backbone tar file comprises compressed backbone files named: `[cnf_name].backbone.xz`. It is important to note that a compressed CNF file will always share its `[cnf_name]` with its associated compressed backbone file.
 
 In the dual directory, the naming convention remains consistent, but with an added `d_` prefix for each compressed CNF or backbone file to indicate it pertains to a dual CNF formula.