foo.cc: In function 'int main()':
foo.cc:16:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   16 |     scanf("%d%d%d%d",&n,&m,&a,&b);// 输入啊。。。
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:22:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   22 |         scanf("%d%d",&x,&y);
      |         ~~~~~^~~~~~~~~~~~~~
foo.cc:46:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   46 |         scanf("%d%d",&x,&y);
      |         ~~~~~^~~~~~~~~~~~~~

Found 7 testcases.
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