fn main() {
    assert_eq!(only_even_quotient(&vec![5, 9, 2, 8]), 4);
}

fn only_even_quotient(numbers: &Vec<i32>) -> i32 {
    let (a, b) = numbers.iter()
        .flat_map(|n1| numbers.iter().map(move|n2| (n1, n2)))
        .filter(|(a, b)| **b != 0 && *a > *b)
        .find(|(a, b)| *a % *b == 0).unwrap();
    *a / *b
}