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