foo.cc: In function 'int main()':
foo.cc:5:13: warning: unused variable 'a1' [-Wunused-variable]
    5 |         int a1,a2,a3,a4;
      |             ^~
foo.cc:5:16: warning: unused variable 'a2' [-Wunused-variable]
    5 |         int a1,a2,a3,a4;
      |                ^~
foo.cc:5:19: warning: unused variable 'a3' [-Wunused-variable]
    5 |         int a1,a2,a3,a4;
      |                   ^~
foo.cc:5:22: warning: unused variable 'a4' [-Wunused-variable]
    5 |         int a1,a2,a3,a4;
      |                      ^~
foo.cc:7:13: warning: unused variable 'a' [-Wunused-variable]
    7 |         int a[5];
      |             ^

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