#include<stdio.h>
typedef char SType;
//出栈
int pop(SType *s,int top){
if(top==-1){
printf("empty stack\n");
return -1;
}
printf("pop %c\n",s[top]);
return --top;
}
//入栈
int push(SType *s,int top, SType ch){
s[++top]=ch;
printf("push %c\n",s[top]);
return top;
}
int main(){
char s[100];
int top=-1;
top=push(s, top, 'a');
top=push(s, top, 'b');
top=push(s, top, 'c');
top=push(s, top, 'd');
top=pop(s, top);
top=pop(s, top);
top=pop(s, top);
top=pop(s, top);
top=pop(s, top);
return 0;
}