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

#define N 101
#define SMAX 256

// typedef int StackElemType;

typedef char String[SMAX];
typedef int BinaryTreeDataType;
typedef struct binarytreenode BinaryTreeNode;
struct binarytreenode
{
    BinaryTreeNode* LSON;
    BinaryTreeDataType DATA;
    BinaryTreeNode* RSON;
};
struct stackelemtype
{
    BinaryTreeNode* address;
    char tag;
};
typedef struct stackelemtype StackElemType;

struct stack
{
    int top;
    StackElemType Stack[N];
};
typedef struct stack Stack;

void InitStack(Stack *S)
{
    S->top = 0;
}

int IsEmptyStack(Stack *S)
{
    return (S->top == 0);
}

void StackOverflow(void)
{
    printf("Stack overflow detected.\n");
    exit(1);
}

void StackUnderflow(void)
{
    printf("Stack underflow detected.\n");
    exit(1);
}

void PUSH (Stack *S, StackElemType x)
{
    if (S->top == N) StackOverflow();
    else
    {
        ++S->top;
        S->Stack[S->top] = x;
    }
}

void POP (Stack *S, StackElemType *x)
{
    if (S->top == 0) StackUnderflow();
    else
    {
        *x = S->Stack[S->top];
        --S->top;
    }
}