#include <stdio.h>
#include <string.h>
class List {
        List* _before;
        static List* _after;
        char _data;
public:
        List(char c) {
                _before = this;
                if (_after == 0) _after = this;
                _data = c;
        }
        List* insert(List* x) {
                x->_before = this;
                x->_after = _after;
                _after->_before = x;
                _after = x;
                return x;
        }
        void print() {
		List *tmp = _after->_before;
                while (tmp != this) {
                        putchar(tmp->_data);
                        tmp = tmp->_before;
                }
                putchar(tmp->_data);
                putchar('\n');
        }
};
List *List::_after = 0;
void main()
{
        char *s = strdup("9214757");
        List* aNode = new List('9');
        for (int i = 0; i < 7; i++) {
                aNode = aNode->insert(new List(s[i]));
        }
        aNode->print();
}