/in/foo.cc: In function 'int main()':
/in/foo.cc:18:11: warning: unused variable 'x2' [-Wunused-variable]
  int x,x1,x2;
           ^~
/in/foo.cc: In function 'bool isPrime(int)':
/in/foo.cc:14:1: warning: control reaches end of non-void function [-Wreturn-type]
 } 
 ^