foo.cc: In function 'int main()':
foo.cc:31:31: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
             if((i >> stage)&1 == 0) continue;
                             ~~^~~~
foo.cc:34:35: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
                     if((i >> u)&1 == 0) continue;
                                 ~~^~~~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。