/in/foo.cc: In function 'int fen(int, int)':
/in/foo.cc:12:9: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
   if(m=n) return fen(m,n-1)+1;
         ^
/in/foo.cc:14:1: warning: control reaches end of non-void function [-Wreturn-type]
 }                                                                          
 ^