#include<stdio.h>

int top=-1;
int arr[20];

int isFull(){
    if(top==size-1)
        return 1;
    else
        return 0;
}

void push(int num){
    if(isFull())
        printf("full");
    else
        arr[++top]=num;
}

int isEmpty(){
    if(top==-1)
        return 1;
    else
        return 0;
}

void pop(){
    if(isEmpty()){
        printf("Stack Underflow");
    else
        top--; 
    }
}

int peek(){
    if(isEmpty())
        printf("Stack Underflow");
    else
        return arr[top];
}

void display(){
    int i;
    for(i=0;i<top;i++){
        printf("%d ",arr[i]);
    }
    printf("\n");
}

int main(){
    int size,i,num;
    char choice[20];
    scanf("%d\n",&size);
    if(size<0){
        printf("Invalid input");
        return 0;
    }
    for(i=0;i<size;i++){
        scanf("%s ",&choice);
        switch(choice){
            case "PUSH":
                scanf("%d",&num);
                push(num);
                break;
            case "POP":
                pop();
                break;
            case "PEEK":
                peek();
                break;
            case "DISPLAY":
                display();
                break;
            default:
                printf("Invalid input");
        }
    }
}