#include <stdio.h>
#include <stdlib.h>

struct node {
    int value;
    struct node *next;
    struct node *prev;
};

void push(int date, struct node **pptop) {
    struct node elem;
    if(*pptop == NULL) {
        *pptop = &elem;
        elem.value = date;
        elem.next = NULL;
    } else {
        (**pptop).next = &elem;
        (*pptop) = &elem;
        elem.value = date;
        elem.next = NULL;
    }
}

int main() {
    struct node *ptop = NULL;
    push(3, &ptop);
    push(5, &ptop);
    push(7, &ptop);

    printf("%d\n", (*ptop).value);


}