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