foo.cc: In function 'void gao(int, int, int)':
foo.cc:8:11: warning: unused variable 'b' [-Wunused-variable]
    8 |     int a,b,c=0,y=x;
      |           ^
foo.cc: In function 'void get_sg(int)':
foo.cc:16:13: warning: unused variable 'c' [-Wunused-variable]
   16 |     int a,b,c;
      |             ^

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