foo.cc: In function 'int main()':
foo.cc:63:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
     freopen("chess.in","r",stdin);
     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
     freopen("chess.out","w",stdout);
     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:65:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d%d",&n,&m,&k,&t);
     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:72:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&tmp);
         ~~~~~^~~~~~~~~~~

[Hydro](https://hydro.ac)提供评测服务