foo.cc: In function 'int main()':
foo.cc:47:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d\n",&n,&m);
  ~~~~~^~~~~~~~~~~~~~~~
foo.cc:51:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d",&a[i]);
             ~~~~~^~~~~~~~~~~~
foo.cc:56:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d\n",&l,&r);
   ~~~~~^~~~~~~~~~~~~~~~

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