#include <stdio.h>
#define N 10

int stack[N];
int current = -1;

int shift() {
    if(current < 0)
    {
        return -1;
    }
    else
    {
        int tmp = stack[0];
        for(int i = 0; i < current; i++)
        {
            stack[i] = stack[i+1];
        }
        stack[current] = 0;
        current--;
        return tmp;
    }
}

void push(int value) {
    if(current >= 9)
    {
        printf("Buffer overflow\n");
        return;
    }
    else
    {
        current++;
        stack[current] = value;
    }
}

void list() {
    for(int i = 0; i<=current; i++)
    {
        printf("%d, ", stack[i]);
    }
    printf("\n");
}

int main() {
    printf("shift(); %d\n", shift());
    for (int i = 0; i < 11; i++) {
        push(i);
    }
    list();
    printf("shift(); %d\n", shift());
    return 0;
}