foo.cc: In function 'int main()':
foo.cc:26:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d%d",&n,&m,&x1,&x2);
  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:28:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&y[i]);
   ~~~~~^~~~~~~~~~~~
foo.cc:33:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&yy[i]);
   ~~~~~^~~~~~~~~~~~~

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