#include<stdio.h>
#include<stdlib.h>
int top=-1,size=5;
int arr[25];
int isfull(){
    if(top==size-1)
        return 1;
    
    else
        return 0;
    
}
void PUSH(int num){
    if(isfull()){
        printf("stack is full \n");
    }
    else{
        arr[++top]=num;
    }
}
int isempty(){
    if(top==-1){
        return 1;
    }
    else{
        return 0;
    }
}
void POP(){
    if(isempty()){
        printf("Stack is empty \n");
    }
    else{
        top--;
    }
}
int PEEK(){
    if(isempty())
        return -1;
        else
            return arr[top];        
}
void traverse(){
    for(int i=0;i<=top;i++){
        printf("%d ",arr[i]);
        printf("\n");
    }
}
int main(){
    int choice,num;
    while(1)
{
    scanf("%d",&choice);
    switch(choice){
        case 1:
        scanf("%d",&num);
        PUSH(num);
        break;
        case 2:
        po();
        break;
        case 3:
        int ans=peek();
        if(ans==-1)
        printf("Stack is empty \n");
        else{
            printf("%d \n",ans);
            break;
        }
        case 4:
        traverse();
        break;
        case 5:
        exit(0);
        default:
        printf("Invalid input");
    }
}}