foo.cc: In function 'int main()':
foo.cc:27:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld%lld%lld%lld",&n,&m,&x1,&x2);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:29:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld",&y[i]);
   ~~~~~^~~~~~~~~~~~~~
foo.cc:34:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld",&yy[i]);
   ~~~~~^~~~~~~~~~~~~~~

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