AtCoder Beginner Contest 298 D

https://atcoder.jp/contests/abc298/tasks/abc298_d

剰余を用意して、1なら10倍して足して、2なら数字×10のべき乗を引けばいいのですが、Rustには負数の剰余を取ると負になるというトラップがありますね。

// Writing a Numeral
#![allow(non_snake_case)]


//////////////////// constants ////////////////////

const D: i64 = 998244353;


//////////////////// library ////////////////////

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>().split_whitespace()
            .map(|e| e.parse().ok().unwrap()).collect()
}


//////////////////// process ////////////////////

fn create_pows(b: i64, n: i32) -> Vec<i64> {
    let mut pows: Vec<i64> = (0..n).map(|_| 1).collect();
    for i in 1..(n as usize) {
        pows[i] = pows[i-1] * b % D
    }
    pows
}

fn f(Q: i32) {
    let mut a: Vec<i64> = (0..Q+1).map(|_| 1).collect();
    let pows: Vec<i64> = create_pows(10, Q+1);
    let mut first: usize = 0;
    let mut last: usize = 1;
    let mut n: i64 = 1;
    for _ in 0..Q {
        let v: Vec<i64> = read_vec();
        if v[0] == 1 {
            a[last] = v[1];
            n = (n * 10 + v[1]) % D;
            last += 1
        }
        else if v[0] == 2 {
            n = (n - a[first] * pows[last-first-1]) % D;
            if n < 0 {
                n += D
            }
            first += 1
        }
        else {
            println!("{}", n);
        }
    }
}

fn main() {
    let Q: i32 = read();
    f(Q)
}