foo.cc: In function 'int main()':
foo.cc:36:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   36 |  scanf("%d%d", &n, &k);
      |  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:37:46: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   37 |  for (register int i = 0; i < n; i ++ ) scanf("%d", a + i);
      |                                         ~~~~~^~~~~~~~~~~~~

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