View Compilation Error

0_0_10963315_30939.cpp: In function `int main()':
0_0_10963315_30939.cpp:71: error: no match for 'operator=' in 'it = (&S)->std::set<_Key, _Compare, _Alloc>::erase [with _Key = node, _Compare = compp, _Alloc = std::allocator<node>](it)'
GCC/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_tree.h:220: note: candidates are: std::_Rb_tree_const_iterator<node>& std::_Rb_tree_const_iterator<node>::operator=(const std::_Rb_tree_const_iterator<node>&)
0_0_10963315_30939.cpp:78: error: no match for 'operator=' in 'it = (&S)->std::set<_Key, _Compare, _Alloc>::erase [with _Key = node, _Compare = compp, _Alloc = std::allocator<node>](it)'
GCC/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_tree.h:220: note: candidates are: std::_Rb_tree_const_iterator<node>& std::_Rb_tree_const_iterator<node>::operator=(const std::_Rb_tree_const_iterator<node>&)