#![allow(unused_imports, unused_macros)] use kyoproio::*; use std::{ collections::*, io::{self, prelude::*}, iter, mem::{replace, swap}, }; fn run(mut kin: I, mut out: O) { macro_rules! output { ($($args:expr),+) => { write!(&mut out, $($args),+).unwrap(); }; } macro_rules! outputln { ($($args:expr),+) => { output!($($args),+); outputln!(); }; () => { output!("\n"); if cfg!(debug_assertions) { out.flush().unwrap(); } } } let n: usize = kin.input(); let a: Vec<_> = kin.iter::().take(n + 1).map(|x| mint(x)).collect(); let mut sb = mint(0); let mut ans = mint(0); for (b, &a) in kin.iter::().take(n + 1).map(|x| mint(x)).zip(a.iter().rev()) { sb += b; ans += a * sb; } outputln!("{}", ans); } fn mint>(x: T) -> ModInt { ModInt::new(x.into(), Mod1e9p7) } pub trait Modulo: Copy { fn modulo(&self) -> i32; } #[derive(Copy, Clone, Eq, PartialEq)] struct Mod998244353; impl Modulo for Mod998244353 { fn modulo(&self) -> i32 { 998244353 } } #[derive(Copy, Clone, Eq, PartialEq)] struct Mod1e9p7; impl Modulo for Mod1e9p7 { fn modulo(&self) -> i32 { 1e9 as i32 + 7 } } #[derive(Copy, Clone, Eq, PartialEq)] struct VarMod(i32); impl Modulo for VarMod { fn modulo(&self) -> i32 { self.0 } } #[derive(Copy, Clone, Eq, PartialEq)] pub struct ModInt(i32, M); impl ModInt { pub fn new(x: i32, m: M) -> Self { debug_assert!(x < m.modulo()); Self(x, m) } pub fn value(&self) -> i32 { self.0 } pub fn inv(&self) -> Self { self.pow((self.m() - 2) as u64) } pub fn pow(&self, mut n: u64) -> Self { let mut x = *self; let mut y = Self(1, self.1); while n > 0 { if n & 1 == 1 { y *= x; } x *= x; n >>= 1; } y } fn m(&self) -> i32 { self.1.modulo() } } use std::{fmt, ops}; impl ops::Neg for ModInt { type Output = Self; fn neg(self) -> Self { Self(if self.0 == 0 { 0 } else { self.m() - self.0 }, self.1) } } impl ops::AddAssign for ModInt { fn add_assign(&mut self, rhs: Self) { self.0 += rhs.0; if self.0 >= self.m() { self.0 -= self.m(); } } } impl ops::SubAssign for ModInt { fn sub_assign(&mut self, rhs: Self) { self.0 -= rhs.0; if self.0 < 0 { self.0 += self.m(); } } } impl ops::MulAssign for ModInt { fn mul_assign(&mut self, rhs: Self) { self.0 = (self.0 as u32 as u64 * rhs.0 as u32 as u64 % self.m() as u32 as u64) as i32; } } impl ops::DivAssign for ModInt { fn div_assign(&mut self, rhs: Self) { assert_ne!(rhs.value(), 0); *self *= rhs.inv(); } } macro_rules! op_impl { ($($Op:ident $op:ident $OpAssign:ident $op_assign:ident)*) => { $(impl ops::$OpAssign for ModInt { fn $op_assign(&mut self, rhs: i32) { self.$op_assign(Self::new(rhs, self.1)); } } impl ops::$Op for ModInt { type Output = Self; fn $op(self, rhs: Self) -> Self { let mut res = self; ops::$OpAssign::$op_assign(&mut res, rhs); res } })* }; } op_impl! { Add add AddAssign add_assign Sub sub SubAssign sub_assign Mul mul MulAssign mul_assign Div div DivAssign div_assign } impl fmt::Display for ModInt { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { self.0.fmt(f) } } impl fmt::Debug for ModInt { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f.pad("ModInt(")?; self.0.fmt(f)?; f.pad(")") } } // ----------------------------------------------------------------------------- fn main() -> io::Result<()> { std::thread::Builder::new() .stack_size(64 * 1024 * 1024) .spawn(|| { run( KInput::new(io::stdin().lock()), io::BufWriter::new(io::stdout().lock()), ) })? .join() .unwrap(); Ok(()) } // ----------------------------------------------------------------------------- pub mod kyoproio { use std::io::prelude::*; pub trait Input { fn bytes(&mut self) -> &[u8]; fn str(&mut self) -> &str { std::str::from_utf8(self.bytes()).unwrap() } fn input(&mut self) -> T { T::input(self) } fn iter(&mut self) -> Iter { Iter(self, std::marker::PhantomData) } fn seq>(&mut self, n: usize) -> B { self.iter().take(n).collect() } } pub struct KInput { src: R, buf: Vec, pos: usize, len: usize, } impl KInput { pub fn new(src: R) -> Self { Self { src, buf: vec![0; 1 << 16], pos: 0, len: 0, } } } impl Input for KInput { fn bytes(&mut self) -> &[u8] { loop { while let Some(delim) = self.buf[self.pos..self.len] .iter() .position(|b| b.is_ascii_whitespace()) { let range = self.pos..self.pos + delim; self.pos += delim + 1; if delim > 0 { return &self.buf[range]; } } if self.pos > 0 { self.buf.copy_within(self.pos..self.len, 0); self.len -= self.pos; self.pos = 0; } if self.len >= self.buf.len() { self.buf.resize(2 * self.buf.len(), 0); } let read = self.src.read(&mut self.buf[self.len..]).unwrap(); if read == 0 { let range = self.pos..self.len; self.pos = self.len; return &self.buf[range]; } self.len += read; } } } pub struct Iter<'a, T, I: ?Sized>(&'a mut I, std::marker::PhantomData<*const T>); impl<'a, T: InputParse, I: Input + ?Sized> Iterator for Iter<'a, T, I> { type Item = T; fn next(&mut self) -> Option { Some(self.0.input()) } } pub trait InputParse: Sized { fn input(src: &mut I) -> Self; } impl InputParse for Vec { fn input(src: &mut I) -> Self { src.bytes().to_owned() } } macro_rules! from_str_impl { { $($T:ty)* } => { $(impl InputParse for $T { fn input(src: &mut I) -> Self { src.str().parse::<$T>().unwrap() } })* } } from_str_impl! { String char bool f32 f64 } macro_rules! parse_int_impl { { $($I:ty: $U:ty)* } => { $(impl InputParse for $I { fn input(src: &mut I) -> Self { let f = |s: &[u8]| s.iter().fold(0, |x, b| 10 * x + (b & 0xf) as $I); let s = src.bytes(); if let Some((&b'-', t)) = s.split_first() { -f(t) } else { f(s) } } } impl InputParse for $U { fn input(src: &mut I) -> Self { src.bytes().iter().fold(0, |x, b| 10 * x + (b & 0xf) as $U) } })* }; } parse_int_impl! { isize:usize i8:u8 i16:u16 i32:u32 i64:u64 i128:u128 } macro_rules! tuple_impl { ($H:ident $($T:ident)*) => { impl<$H: InputParse, $($T: InputParse),*> InputParse for ($H, $($T),*) { fn input(src: &mut I) -> Self { ($H::input(src), $($T::input(src)),*) } } tuple_impl!($($T)*); }; () => {} } tuple_impl!(A B C D E F G); macro_rules! array_impl { { $($N:literal)* } => { $(impl InputParse for [T; $N] { fn input(src: &mut I) -> Self { let mut arr = std::mem::MaybeUninit::uninit(); unsafe { let ptr = arr.as_mut_ptr() as *mut T; for i in 0..$N { ptr.add(i).write(src.input()); } arr.assume_init() } } })* }; } array_impl! { 1 2 3 4 5 6 7 8 } #[macro_export] macro_rules! kdbg { ($($v:expr),*) => { if cfg!(debug_assertions) { dbg!($($v),*) } else { ($($v),*) } } } }