foo.cc: In function 'int f(int, int)':
foo.cc:24:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
 while(t=a%b)
       ~^~~~
foo.cc: In function 'int main()':
foo.cc:6:12: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
 int x;scanf("%d",&x);
       ~~~~~^~~~~~~~~