foo.cc: In function 'int main()':
foo.cc:21:9: warning: variable 'num' set but not used [-Wunused-but-set-variable]
   21 |     int num;
      |         ^~~
foo.cc:22:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |     scanf("%d",&n);
      |     ~~~~~^~~~~~~~~
foo.cc:25:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   25 |         scanf("%d %d %d %d",&a0,&a1,&b0,&b1);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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