foo.cc: In function 'int main()':
foo.cc:6:18: warning: format '%lf' expects argument of type 'double*', but argument 2 has type 'double' [-Wformat=]
    6 |         scanf("%lf",a);
      |                ~~^  ~
      |                  |  |
      |                  |  double
      |                  double*
foo.cc:6:14: warning: 'a' is used uninitialized [-Wuninitialized]
    6 |         scanf("%lf",a);
      |         ~~~~~^~~~~~~~~

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