#include <stdio.h>
#include <stdint.h>
#include <string.h>
#define MAX 10
char cmd[20];
void process_stack(int n) {
// Your logic here
int stack[MAX];
int val;
int count=-1;
for(int i=0;i<n;i++){
scanf("%s", cmd);
if(strcmp(cmd,"push")==0){
if(count>=MAX-1){
printf("Stack Overflow\n");
continue;
}
scanf("%d", &val);
count++;
stack[count]=val;
}
else{
if(count<0){
printf("Stack Underflow\n");
continue;
}
val=stack[count];
printf("%d\n", val);
count--;
}
}
}
int main() {
int n;
scanf("%d", &n);
getchar(); // Consume newline after number
process_stack(n);
return 0;
}