/in/foo.cc: In function 'int del(int, int)':
/in/foo.cc:113:6: warning: unused variable 'l' [-Wunused-variable]
  int l,r;
      ^
/in/foo.cc:113:8: warning: unused variable 'r' [-Wunused-variable]
  int l,r;
        ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:171:8: warning: unused variable 'flag' [-Wunused-variable]
    int flag=del(root,x);
        ^~~~

ValueError("invalid literal for int() with base 10: ''",)