q082.rs

const MOD: i128 = 1_000_000_007;

fn main() {
  proconio::input!{ l: i128, r: i128, };
  let mut ans = 0;
  for i in 0..=18 {
    let min = 10i128.pow(i).max(l);
    let max = (10i128.pow(i + 1) - 1).min(r);
    if min <= max {
      ans += (i as i128 + 1) * (min + max) * (max - min + 1) / 2;
      ans %= MOD;
    }
  }
  println!("{}", ans);
}