use std::collections::VecDeque;

let mut int_queue = VecDeque::new();
int_queue.push_back(1);
int_queue.push_back(3);
int_queue.push_back(5);

let top = int_queue[0];
//top is 1
let first = int_queue.pop_front();
//first is Some(1)
let second = int_queue.pop_front();
//second is Some(3)
let third = int_queue.pop_front();
//third is Some(5)

println!("top is {:?}", top);      
println!("first is {:?}", first);  
println!("second is {:?}", second);    
println!("third is {:?}", third);