import sys
s = input()
t = input()
table = [[len(s) for i in range(len(s))] for j in range(26)]

for i in range(len(s)):
  table[ord(s[i])-97][i] = 0
for i in range(26):
  for j in range(len(s)):
    table[i][len(s)-j-2] = min(table[i][len(s)-j-1] +1, table[i][len(s)-j-2])
  for j in range(len(s)):
    table[i][len(s)-j-2] = min(table[i][len(s)-j-1] +1, table[i][len(s)-j-2])

for letter in t:
  if s.find(letter) == -1:
    print(-1)
    sys.exit()
    
place = 0
ans = 0
for i in range(len(t)):
  letter = t[i]
  move = table[ord(t[i])-97][place]
  ans += move + 1
  place = (place + move+1)%len(s)
print(ans)