foo.cc: In function 'int main()':
foo.cc:24:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.cc:18:17: note: 'c' was declared here
  double a=1,b=1,c;
                 ^
foo.cc:24:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^
foo.cc:18:17: note: 'c' was declared here
  double a=1,b=1,c;
                 ^
foo.cc: In function 'int FBNQ(long long int)':
foo.cc:24:9: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized]
  return c;
         ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。