#include <stdio.h>
#include <stdlib.h>
 
struct node {
    char c;
    struct node* p;
};
 
struct node* func(char* s) {
    struct node* h = NULL, *n;
    
    while(*s) {
        n = malloc(sizeof(struct node));
        n->c = *s++;
        n->p = h;
        h = n;
    }
    
    return h;
}
 
int main() {
    struct node* n = func("BEST");
    
    while(n) {
        putchar(n->c);
        struct node* t = n;
        n = n->p;
        free(t);
    }
    
    return 0;
}