Monistus

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

void recursion(){

}

int main(){
    string remaining;
    cin >> remaining;
    reverse(remaining.begin(), remaining.end());

    string print;
    while(!remaining.empty()){
        char c = remaining.back();
        remaining.pop_back();

        if(isdigit(c)){
            int digit = int(c) - '0';
            string newstring = remaining.substr(remaining.length() - digit, digit);
            remaining += newstring;
        }
        else
            print += c;
    }

    cout << print;
}

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