#include <stdio.h>
#include <stdint.h>
#include <string.h>
#define MAX 10
void process_stack(int n) {
// Your logic here
int v[MAX], index = 0;
char s[5];
int x;
while(n--){
scanf("%s", s);
scanf("%d", &x);
if(strcmp(s,"push") == 0){
if(index<MAX){
v[index] = x;
index++;
} else printf("Stack Overflow\n");
} else if(strcmp(s,"pop") == 0){
if(index > 0){
printf("%i\n", v[index - 1]);
index--;
} else printf("Stack Underflow\n");
}
}
}
int main() {
int n;
scanf("%d", &n);
getchar(); // Consume newline after number
process_stack(n);
return 0;
}