foo.cc: In function 'int main()':
foo.cc:25:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&op);
   ~~~~~^~~~~~~~~~
foo.cc:28:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d",&x,&y);
    ~~~~~^~~~~~~~~~~~~~
foo.cc:34:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d",&l,&r);
    ~~~~~^~~~~~~~~~~~~~

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