Monistus

l = input()
i = -1
while True:
  i+=1
  q = len(l)
  if i == q:
    break
  if q>=(5*(10**5)):
    break
  curr= l[i]
  if curr.isdigit():
    kslice = str((l[(i+1):i+int(curr)+1]))
    true = 0
    j = 0
    while j < len(kslice) and true==0:
      if kslice[j].isdigit():
        i = l.index(kslice[j])-len(kslice)
        if i < -1:
            i = -1
        l=l.replace(str(curr),kslice,1)
        true = 1
        break
      j+=1
    if true == 0:
      l=l.replace(str(curr),kslice,1)
      i+=len(kslice)
  elif i == len(l)-1:
    break
print(l)

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: WRONG ANSWER

Test 12

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 2

Verdict: TIME LIMIT EXCEEDED