foo.cc: In function 'int main()':
foo.cc:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |     scanf("%d%d",&m,&n);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc: In function 'int Acm(int, int)':
foo.cc:17:9: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
   17 |  return a;
      |         ^

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