Monistus

input/code.cpp: In function 'int main()':
input/code.cpp:13:45: warning: comparison of integer expressions of different signedness: 'long unsigned int' and 'int' [-Wsign-compare]
   13 |     if (index != std::string::npos && index < ilen) {
      |                                       ~~~~~~^~~~~~

// speed optimization

#include <string>
#include <iostream>

int main() {
  std::string input;
  std::cin >> input;
  int ilen = 499998;
  unsigned long int index = 0;
  while (true) {
    index = input.find_first_of("123456789", index);
    if (index != std::string::npos && index < ilen) {  
      input.replace(index, 1, input.substr(index+1, input[index] - 48));
    } else {  
      std::cout << input;
      return 0;
    }
  }
  return 1;
}

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: WRONG ANSWER

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: WRONG ANSWER

Test 14

Group: 2

Verdict: TIME LIMIT EXCEEDED