fn min_avg_two_slice(a: &[i64]) -> i64 {
    let mut idx = 0i64;
    let mut min = (a[0] + a[1]) as f64 / 2.0;

    for i in 0..a.len() - 1 {
        let mut cur = (a[i] + a[i + 1]) as f64 / 2.0;
        if i + 2 < a.len() {
            let three = (a[i] + a[i + 1] + a[i + 2]) as f64 / 3.0;
            cur = cur.min(three);
        }
        if cur < min {
            min = cur;
            idx = i as i64;
        }
    }

    idx
}