foo.cc: In function 'int low_b(int, int, int)':
foo.cc:21:26: error: 'low_bound' was not declared in this scope
   21 |  if(d[mid]>=val)  return low_bound(l,mid,val);
      |                          ^~~~~~~~~
foo.cc:22:26: error: 'low_bound' was not declared in this scope
   22 |  if(d[mid]<val)   return low_bound(mid+1,r,val);
      |                          ^~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:56:9: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   56 |  freopen("a.in","r",stdin);
      |  ~~~~~~~^~~~~~~~~~~~~~~~~~

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