Monistus

#include <bits/stdc++.h>

using namespace std;

string ans;

void rec(string s) {
    int len=s.size();
    for (int i=0; i<len; i++) {
        int cur=s[i]-'0';
        if (cur>=1 && cur <=9) {
            int d=len-(i+1);
            int to_take=min(cur, d);
            string news = s.substr(i+1, to_take);
            if (to_take<cur) {
                to_take=cur-to_take;
                string startpart=s.substr(0,to_take);
                news+=startpart;
            }
            rec(news);
        } else {
            ans+=s[i];
        }
    }
}

int main()
{
    string s;
    cin >> s;
    rec(s);
    cout << ans;
}

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: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED