Monistus

#include <bits/stdc++.h>
using namespace std;

int main() {
    string lause;
    cin >> lause;

    long unsigned int i = 0;
    string bef, aft;
    string ala = "";
    while(i < lause.length()) {
        if(isdigit(lause[i])) {
            bef = lause.substr(0, i);
            ala = lause.substr(i+1, lause[i] - '0');
            aft = "";
            if(i != lause.length() - 1) {
                aft = lause.substr(i + 1, lause.length() - (i+1));
            }
            lause = bef + ala + aft;
        }
        else {
            i++;
        }
    }

    cout << lause;
}

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