/*
#include <stdio.h>
int stack[201]={};
int top=-1;
void push(int data) {
top++;
stack[top] = data;
}
int pop() {
if (top != -1) {
return stack[top--];
}
}
int main()
{
int n;
char arr[201]={};
scanf("%d\n",&n);
for (int i=1 ; i<=n ; i++){
gets(arr);
if (arr[0] == 't') {
if (top == -1) {
printf("-1\n");
}
else {
printf("%d\n", stack[top]);
}
}
else if (arr[1] == 'u') {
int num=0;
for(int j=6 ; arr[j]!=' ' ; j++) {
num=num*10+arr[j] - 48;
}
push(num);
}
else if (arr[0] == 'p') {
if (top != -1) {
top--;
}
}
else if (arr[0] == 's') {
printf("%d\n", top+1);
}
else if (arr[0] == 'e') {
if (top == -1) {
printf("true\n");
}
else {
printf("false\n");
}
}
}
}
*/
#include<stdio.h>
int queue[201]={};
int front = 0;
int back = 0;
void push(int data) {
back++;
queue[back] = data;
}
int pop() {
if(front != back) {
return queue[front++];
}
else {
front=0;
back=0;
}
}
int main() {
int n;
char arr[201]={};
scanf("%d\n",&n);
for(int i=1 ; i<=n ; i++) {
gets(arr);
if (arr[0] == 'b') {
if (back == 0) {
printf("-1\n");
}
else {
printf("%d\n", queue[back]);
back--;
}
}
else if (arr[1] == 'u') {
int a=0;
for(int j=6 ; arr[j]!=' ' ; j++) {
a=a*10+arr[j] - 48;
}
push(a);
}
else if (arr[0] == 'p') {
pop();
}
else if (arr[0] == 's') {
printf("%d\n", back+1);
}
else if(arr[0] == 'e') {
if(back == 0) {
printf("true\n");
}
else {
printf("false\n");
}
}
else if(arr[0] == 'f') {
if(front == 0) {
printf("-1\n");
}
else {
printf("%d\n",queue[front]);
}
}
}
}