import sys
import numpy as np
import bisect
s = input()
t = input()



count = 0
s_len = len(s)
s_list = np.zeros(len(s))
t_list = []*len(t)
indexes = []

for i in range(26):
  
  indexes.append([j for j, x in enumerate(s) if x == chr(i + ord('a')) ])
  

for i,k in enumerate(t):

  index = indexes[ord(k)-97]
  
  if len(indexes) == 0:
    print(-1)
    sys.exit(0)
  else:
    t_list.insert(i,index)
    


pre = -1
for i in range(len(t)):
  
  #high = [j  for j in t_list[i] if j > pre]
  high = bisect.bisect_left(t_list[i], pre) 

  if high >= len(t_list[i]):
    
    count += s_len - pre  + t_list[i][0]
    pre = t_list[i][0] 
  else:
    
    count += t_list[i][high] - pre 
    pre = t_list[i][high]

print(count)