let numbers = [2, 3, 5, 7, 11, 13, 17];
let contain2 = numbers.contains(&2);
//contain2 is true
let contain4 = numbers.contains(&4);
//contain4 is false
let index5 = numbers.iter()
.position(|&x| x == 5)
.unwrap();
//index5 is 2
println!("contain2 is {contain2}");
println!("contain4 is {contain4}");
println!("index5 is {index5}");