struct Node
{
    char *data;
    struct Node *link;
};
struct Node *top;

// Utility function to add an element data in the stack
// insert at the beginning
void push(char *data)
{
    // create new node temp and allocate memory
    struct Node *temp;
    temp = (struct Node *)malloc(sizeof(struct Node));

    // check if stack (heap) is full. Then inserting an element would
    // lead to stack overflow
    if (!temp)
    {
        printf("\nHeap Overflow");
        abort;
    }

    // initialize data into temp data field
    temp->data = data;

    // put top pointer reference into temp link
    temp->link = top;

    // make temp as top of Stack
    top = temp;
}

// Utility function to check if the stack is empty or not
int isEmpty()
{
    return top == NULL;
}

// Utility function to return top element in a stack
char *peek()
{
    // check for empty stack
    if (!isEmpty(top))
        return top->data;
    else
        abort();
}

// Utility function to pop top element from the stack

void pop()
{
    struct Node *temp;

    // check for stack underflow
    if (top == NULL)
    {
        printf("\nStack Underflow");
        abort();
    }
    else
    {
        // top assign into temp
        temp = top;

        // assign second node to top
        top = top->link;

        // destroy connection between first and second
        temp->link = NULL;

        // release memory of top node
        free(temp);
    }
}

void display() // remove at the beginning
{
    struct Node *temp;

    // check for stack underflow
    if (top == NULL)
    {
        printf("\nStack Underflow");
        abort();
    }
    else
    {
        temp = top;
        printf("Stack contains:\n");
        while (temp != NULL)
        {

            // print node data
            printf("%s\n", temp->data);

            // assign temp link to temp
            temp = temp->link;
        }
    }
}