#include<stdio.h>
#include<stdlib.h> 
#define MAX_SIZE 5
int stack[MAX_SIZE];
int top = -1; 
void push(int data) 
{
    if(top==MAX_SIZE-1) 
    {
        printf("Stack overflow\n");
    }
    else
    {
        top++;
        stack[top]=data;
    }
}
void peek()
{
    if(top==-1)
    {
        printf("Stack is empty\n");
    }
    else
    {
        printf("%d\n", stack[top]);
    }
}
int main() 
{
    int n,data;
    char command[10];
    scanf("%d",&n); 
    for(int i=0;i<n;i++) 
    {
        scanf("%s",command); 
        if(strcmp(command,"push")==0)
        {
            if(scanf("%d",&data)==1)
            { 
                push(data);
            } 
            else 
            {
                printf("Invalid input\n");
                exit(1);
            }
        }
        else if(strcmp(command,"peek")==0) 
        {
            peek();
        } 
        else
        {
            printf("Invalid input\n");
        }
    }
    return 0;
}