#[allow(unused_imports)] use std::io::{stdout, BufWriter, Write}; fn main() { let out = stdout(); let mut out = BufWriter::new(out.lock()); inputv! { n:usize, } let t = input_vector::(); let mut ans = 0; for i in 0..n { let left = i + 1; let right = n - i; ans += t[i] * left * right; } writeln!(out, "{}", ans).unwrap(); } //https://github.com/manta1130/competitive-template-rs use input::*; pub mod input { use std::cell::RefCell; use std::io; pub const SPLIT_DELIMITER: char = ' '; pub use std::io::prelude::*; #[macro_export] thread_local! { pub static INPUT_BUFFER:RefCell>=RefCell::new(std::collections::VecDeque::new()); } #[macro_export] macro_rules! input_internal { ($x:ident : $t:ty) => { INPUT_BUFFER.with(|p| { if p.borrow().len() == 0 { let temp_str = input_line_str(); let mut split_result_iter = temp_str .split(SPLIT_DELIMITER) .map(|q| q.to_string()) .collect::>(); p.borrow_mut().append(&mut split_result_iter) } }); let mut buf_split_result = String::new(); INPUT_BUFFER.with(|p| buf_split_result = p.borrow_mut().pop_front().unwrap()); let $x: $t = buf_split_result.parse().unwrap(); }; (mut $x:ident : $t:ty) => { INPUT_BUFFER.with(|p| { if p.borrow().len() == 0 { let temp_str = input_line_str(); let mut split_result_iter = temp_str .split(SPLIT_DELIMITER) .map(|q| q.to_string()) .collect::>(); p.borrow_mut().append(&mut split_result_iter) } }); let mut buf_split_result = String::new(); INPUT_BUFFER.with(|p| buf_split_result = p.borrow_mut().pop_front().unwrap()); let mut $x: $t = buf_split_result.parse().unwrap(); }; } #[macro_export] macro_rules! inputv { ($i:ident : $t:ty) => { input_internal!{$i : $t} }; (mut $i:ident : $t:ty) => { input_internal!{mut $i : $t} }; ($i:ident : $t:ty $(,)*) => { input_internal!{$i : $t} }; (mut $i:ident : $t:ty $(,)*) => { input_internal!{mut $i : $t} }; (mut $i:ident : $t:ty,$($q:tt)*) => { input_internal!{mut $i : $t} inputv!{$($q)*} }; ($i:ident : $t:ty,$($q:tt)*) => { input_internal!{$i : $t} inputv!{$($q)*} }; } pub fn input_all() { INPUT_BUFFER.with(|p| { if p.borrow().len() == 0 { let mut temp_str = String::new(); std::io::stdin().read_to_string(&mut temp_str).unwrap(); let mut split_result_iter = temp_str .split_whitespace() .map(|q| q.to_string()) .collect::>(); p.borrow_mut().append(&mut split_result_iter) } }); } pub fn input_line_str() -> String { let mut s = String::new(); io::stdin().read_line(&mut s).unwrap(); s.trim().to_string() } #[allow(clippy::match_wild_err_arm)] pub fn input_vector() -> Vec where T: std::str::FromStr, { let mut v: Vec = Vec::new(); let s = input_line_str(); let split_result = s.split(SPLIT_DELIMITER); for z in split_result { let buf = match z.parse() { Ok(r) => r, Err(_) => panic!("Parse Error",), }; v.push(buf); } v } #[allow(clippy::match_wild_err_arm)] pub fn input_vector_row(n: usize) -> Vec where T: std::str::FromStr, { let mut v = Vec::with_capacity(n); for _ in 0..n { let buf = match input_line_str().parse() { Ok(r) => r, Err(_) => panic!("Parse Error",), }; v.push(buf); } v } pub trait ToCharVec { fn to_charvec(&self) -> Vec; } impl ToCharVec for String { fn to_charvec(&self) -> Vec { self.to_string().chars().collect::>() } } }