fn main() {
    let mut xx = String::new();
    std::io::Read::read_to_string(&mut std::io::stdin(), &mut xx).ok();
    let xx: Vec<usize> = xx.split_whitespace().skip(1).flat_map(str::parse).collect();

    let n = xx.len();

    let answer = xx
        .iter()
        .enumerate()
        .map(|(i, &x)| (i + 1) * (n - i) * x)
        .sum::<usize>();

    println!("{answer}");
}