projecteuler.net/048/main.rs

// https://rob.co.bb/posts/2019-02-10-modular-exponentiation-in-rust/
fn mod_pow(mut base: u128, mut exp: u128, modulus: u128) -> u128 {
    if modulus == 1 { return 0 }
    let mut result = 1;
    base = base % modulus;
    while exp > 0 {
        if exp % 2 == 1 {
            result = result * base % modulus;
        }
        exp = exp >> 1;
        base = base * base % modulus
    }
    result
}


fn main() {
    let m = 10000000000;
    let mut res = 0u128;
    for n in 1..1000 {
        let t = mod_pow(n, n, m);
        res += t;
        res = res % m;
    }
    println!("{}", res);
}