#include<stdio.h>
#include<string.h>
int top=-1;

int push(int val,int *arr,int size){
    if(top==size-1){
        printf("Stack Oveflow");
    }else{
        arr[++top]=val;
    }
}
int pop(int *arr){
    if(top==-1){
        printf("Stack Underflow");
    }else{
        return top--;
    }
}
void display(int size){
    for(int i=size-1;i<=1;i--){
        printf("%d ",arr[i]);
    }
}
void peek(int *arr){
    printf("%d",arr[top]);
}
int main(){
    int size;
    scanf("%d",&size);
    int arr[size];
    char num[20];
    for(int i=0;i<size;i++){
        scanf("%s",num);
        if(strcmp(num,"PUSH")){
            int val;
            scanf("%d",&val);
            push(val,arr,size);
        }else if(strcmp(num,"PUSH")){
            pop(arr);
        }else if(strcmp(num,"DISPLAY"){
            display(size);
        }else{
            peek(arr);
        }
    }
}