/in/foo.cc: In function 'int main()':
/in/foo.cc:22:6: warning: unused variable 'v' [-Wunused-variable]
  int v,u,val,num=0;
      ^
/in/foo.cc:22:8: warning: unused variable 'u' [-Wunused-variable]
  int v,u,val,num=0;
        ^
/in/foo.cc:22:10: warning: unused variable 'val' [-Wunused-variable]
  int v,u,val,num=0;
          ^~~