foo.cc: In function 'int main()':
foo.cc:5:15: warning: unused variable 'b' [-Wunused-variable]
    5 |         int a,b,c,d;
      |               ^
foo.cc:5:17: warning: unused variable 'c' [-Wunused-variable]
    5 |         int a,b,c,d;
      |                 ^
foo.cc:5:19: warning: unused variable 'd' [-Wunused-variable]
    5 |         int a,b,c,d;
      |                   ^

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