/in/foo.cc: In function 'data change(data)':
/in/foo.cc:35:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'void dfs(data, long long int, data, long long int)':
/in/foo.cc:61:8: warning: variable 'a' set but not used [-Wunused-but-set-variable]
   data a=_zi,b=(x-1)*X;
        ^
/in/foo.cc:61:14: warning: variable 'b' set but not used [-Wunused-but-set-variable]
   data a=_zi,b=(x-1)*X;
              ^