fn max_double_slice_sum(a: &[i64]) -> i64 {
    let size = a.len();
    if size < 3 {
        return 0;
    }

    let mut p1 = vec![0i64; size];
    let mut p2 = vec![0i64; size];

    for i in 2..size - 1 {
        p1[i] = 0.max(p1[i - 1] + a[i - 1]);
        p2[size - i - 1] = 0.max(p2[size - i] + a[size - i]);
    }

    let mut sum = p1[1] + p2[1];
    for i in 1..size - 1 {
        sum = sum.max(p1[i] + p2[i]);
    }

    sum
}