/in/foo.cc: In function 'int main()':
/in/foo.cc:29:6: warning: unused variable 'n' [-Wunused-variable]
  int n,k,a,b,x,y,f=1;
      ^
/in/foo.cc:29:18: warning: unused variable 'f' [-Wunused-variable]
  int n,k,a,b,x,y,f=1;
                  ^