fn main() {
    let x = vec![1, 1, 2, 3, 5, 5, 8, 13];
    fn bis<P>(ok: i64, ng: i64, p: P) -> i64
        where P: Fn(i64) -> bool {
        let mid = (ok + ng) / 2;
        if (ok - ng).abs() == 1 {
            ok
        } else if p(mid) {
            bis(mid, ng, p)
        } else {
            bis(ok, mid, p)
        }
    }
    let i = bis(x.len() as i64, -1, |i| x[i as usize] >= 5);
    println!("i = {}", i);
    let j = bis(x.len() as i64, -1, |i| x[i as usize] > 5);
    println!("j = {}", j);
}

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