foo.cc: In function 'void build_map()':
foo.cc:12:24: warning: variable 'source' set but not used [-Wunused-but-set-variable]
   12 |         int target = 0,source = i;
      |                        ^~~~~~
foo.cc: In function 'int main()':
foo.cc:26:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   26 |     scanf("%d%d",&n,&m);
      |     ~~~~~^~~~~~~~~~~~~~
foo.cc:27:50: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   27 |     for(int i=0;i<m;i++)for(int j=0;j<n;j++)scanf("%d",&medicine[i][j]);
      |                                             ~~~~~^~~~~~~~~~~~~~~~~~~~~~

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