foo.cc: In function 'int main()':
foo.cc:12:12: error: 'na' was not declared in this scope; did you mean 'ba'?
   12 |   int ba=b;na=n;//找替身，然后用替身来求最大公约数
      |            ^~
      |            ba
foo.cc:5:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    5 |  freopen("data.txt","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:6:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
    6 |  freopen("ans.txt","w",stdout);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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