Monistus

s = list(input()[::-1])
rs = []
n = len(s)
m = 0
 
pos = n-1
 
for i in range(500001-n):
    s.append('0')
 
while pos >= 0:
  if '1'<=s[pos]<='9':
    num = int(s[pos])
    for i in range(num):
      s[pos+num-i-1] = s[pos-i-1]
    pos += num-1
    continue
  rs.append(s[pos])
  pos -= 1
 

print("".join(rs))

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: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED