#include <stdio.h>
#include <stdint.h>
#include <string.h>
#define MAX 10
void process_stack(int n) {
// Your logic here
int buffer [MAX];
int head = 0;
for (int i = 0; i < n ; i++){
char temp[5];
int value;
scanf("%s %d", temp, &value);
if (strcmp(temp, "push")==0){
if (head < MAX){
buffer[head] = value;
head++;
}else {
printf("Stack Overflow\n");
}
}else {
if (head > 0) {
printf ("%d\n",buffer[--head]);
}
else {
printf("Stack Underflow\n");
}
}
}
}
int main() {
int n;
scanf("%d", &n);
getchar(); // Consume newline after number
process_stack(n);
return 0;
}