Monistus

#include <iostream>
#include <sstream>

using namespace std;

string duplicate(string &str)
{
    bool finalWord = false;
    while (!finalWord)
    {
        finalWord = true;
        int index = 0;
        for (char ch : str)
        {
            if (isdigit(ch))
            {
                finalWord = false;
                stringstream ss;
                if (index > 0)
                {
                    ss << str.substr(0, index);
                }
                ss << str.substr(index + 1, int(ch) - 48);
                ss << str.substr(index + 1, str.length() - 1 - index);
                str = ss.str();
                break;
            }
            index++;
        }
    }
    return str;
}
int main()
{
    string word;
    cin >> word;
    cout << duplicate(word);
    return 0;
}

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