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

typedef char* pile;

void push(pile* p, char c) {
    p = (pile*)realloc(p, sizeof(*p) + sizeof(char));
    (*p)[(sizeof(*p)/sizeof(char))-1] = c;
}

char pop(pile* p) {
    char c = (*p)[(sizeof(*p)/sizeof(char))-1];
    p = realloc(p, sizeof(*p) - sizeof(char));
    return c;
}

int empty(pile p) {
    return p[0] == 0;
}

char top(pile p) {
    return p[(sizeof(p)/sizeof(char))-1];
}

void clear(pile* p) {
    p = realloc(p, sizeof(char));
    (*p)[0] = 0; 
}

pile create() {
    pile p = (pile)calloc(1, sizeof(char));
    return p;
}

pile destroy(pile* p) {
    free(p);
}