import sys
from collections import defaultdict
from bisect import bisect_left
s = sys.stdin.readline().strip()
a = sys.stdin.readline().strip()
def getIdx(s, a):
ch2indices = defaultdict(list)
for i, ch in enumerate(s):
ch2indices[ch].append(i)
for ch in a:
if ch not in ch2indices:
return -1
indices = []
continue_seq = ''
ith = 0
sidx = 0
while ith < len(a):
ch = a[ith]
idx = bisect_left(ch2indices[ch], sidx)
if idx != len(ch2indices[ch]):
continue_seq += ch
sidx = ch2indices[ch][idx] + 1
ith += 1
else:
indices.append(sidx)
continue_seq = ''
sidx = 0
if continue_seq:
indices.append(sidx)
total_idx = len(s) * (len(indices) - 1) + indices[-1] - len(a)
return total_idx
print(getIdx(s, a))
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