// editor1
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define MAX 5
int stack[MAX];
int top = - 1;
const char*STACK_OVERFLOW_MSG="Stack overflow\n";
const char*STACK_EMPTY_MSG="Stack is empty\n";
const char*invalid="Invalid Input\n";
int is_valid_integer(const char*str){
    char* endptr;
    strtol(str, &endptr,10);
    return  *endptr=='\0';
}
void push(int x)
{
if(top== MAX -1)
{
    printf("%s",STACK_EMPTY_MSG);
}

 else
 {
    stack[++top]=x;
}
}
void peek()
{
    
if(top== -1){
    printf("%s",STACK_EMPTY_MSG);
}
else{
    printf("%d\n",stack[top]);
}

int main(){
    int n;
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        char cmd[10];
    scanf("%s",cmd);
    if(strcmp (cmd,"push")==0){
        int x;
         if(scanf ("%d",&x)==1) {
           push(x);  
         }
         else
         {
             printf("%s",invalid);
             while(getchar() != '\n');
         }
       else if(strcmp (cmd,"peek")==0){
           peek();
       }
    }
    return 0;
    }
}