foo.cc: In function 'int main()':
foo.cc:8:27: warning: unused variable 'b1' [-Wunused-variable]
    8 |  int a1[3], a2[3], a3[3], b1[3], b2[3];
      |                           ^~
foo.cc:8:34: warning: unused variable 'b2' [-Wunused-variable]
    8 |  int a1[3], a2[3], a3[3], b1[3], b2[3];
      |                                  ^~

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