Monistus

#include <iostream>
#include <cctype>
#include <string>

std::string sana;
std::string::size_type nodigitcounter = 0;
std::string::size_type location = 0;

int main() {
    std::cin >> sana;

    while (nodigitcounter < sana.length()) {
        for (std::string::size_type i = location; i < sana.length(); ++i) {
            if (std::isdigit(sana[i])) {
                sana = sana.substr(0, i) + sana.substr(i + 1, std::stoi(sana.substr(i, 1))) + sana.substr(i + 1);
                location = i;
                break;
            } else {
                nodigitcounter += 1;
            }
        }
    }

    std::cout << sana << std::endl;

    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