foo.cc: In function 'int f(int, int)':
foo.cc:12:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
 while(t=a%b)
       ~^~~~
foo.cc:7:7: warning: unused variable 'n' [-Wunused-variable]
 int t,n=0;
       ^

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