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