/in/foo.cc: In function 'int main()':
/in/foo.cc:5:10: warning: unused variable 'k' [-Wunused-variable]
  int i,j,k,n,a,b;
          ^
/in/foo.cc:5:16: warning: variable 'b' set but not used [-Wunused-but-set-variable]
  int i,j,k,n,a,b;
                ^