#include <stdio.h>
#include <stdint.h>
#include <string.h>
#define MAX 10
void process_stack(int n) {
char str[10];
int arr[MAX];
int top=-1;
for(int i=0;i<n;i++){
scanf("%s",str);
// printf("%d\n",i);
getchar();
if(strcmp(str,"push")==0)
{
int a;
scanf("%d",&a);
if(top<MAX-1){
top++;
arr[top]=a;
//printf("t%d\n",top);
}
else printf("Stack Overflow\n");
}
else if(strcmp(str,"pop")==0)
{
if(top>-1){
printf("%d\n",arr[top]);
top--;
}
else {
printf("Stack Underflow\n");
}
}
}
}
int main() {
int n;
scanf("%d", &n);
getchar(); // Consume newline after number
process_stack(n);
return 0;
}