/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:39:9: error: 'memset' was not declared in this scope
         memset(empty,1,sizeof empty);
         ^~~~~~
/in/foo.cc:39:9: note: suggested alternative: 'wmemset'
         memset(empty,1,sizeof empty);
         ^~~~~~
         wmemset