Monistus

use std::io;

const MAX_SIZE: usize = 5 * 10_usize.pow(5);

fn main() {
    let mut s = String::with_capacity(MAX_SIZE);
    io::stdin().read_line(&mut s).unwrap();

    while let Some(di) = s.find(|c: char| c.is_digit(10)) {
        let d = s[di..].chars().next().unwrap().to_digit(10).unwrap() as usize;
        let slice = &s[di + 1..di + d + 1].to_string();
        s.replace_range(di..di + 1, &slice);
    }

    println!("{}", s);
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 9

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 10

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 11

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 2

Verdict: TIME LIMIT EXCEEDED