foo.cc: In function 'int main()':
foo.cc:54:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   54 | scanf( "%d%d" , &n , &m ) ;
      | ~~~~~^~~~~~~~~~~~~~~~~~~~
foo.cc:56:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   56 | int s , t ; scanf( "%d%d" , &s , &t ) ;
      |             ~~~~~^~~~~~~~~~~~~~~~~~~~

正在同步测试数据，请稍后
[Hydro](https://hydro.ac)提供评测服务