Monistus

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

int main() {
	string mj;
	cin >> mj;
 
	for (long unsigned int i = 1; i <= mj.size(); i++) {
		char ch = mj[i-1];
		if (ch > '0' && ch <= '9') {
			string substring = mj.substr(i, ch-'0'); 
			mj.insert(i, substring);
			mj.erase(i-1, 1);
			i--;
		}
	}
	cout << mj << endl;
}

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: 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