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