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