s = gets.chomp
t = gets.chomp

len = s.length

i = 0
hash = {}
s.chars { |ch|
    if hash.key?(ch)
        hash[ch].push(i)
    else
        hash[ch] = [i]
    end
    i += 1
}

i = 0
t.chars { |ch|
    if hash.key?(ch)
        list = hash[ch]
        pos = i%len
        if list[-1] <= pos
            i += len+list[0] - pos
        else
            list.each { |j|
                if pos < j
                    i += j - pos
                    break
                end
            }
            # head = 0
            # tail = list.size-1
            # mid = (head+tail)/2
            # while head < tail
            #     if list[mid] <= pos
            #         head = mid + 1
            #     else
            #         tail = mid
            #     end
            #     mid = (head+tail)/2
            # end
            # i += list[mid] - pos
        end
    else
        i = -2
        break
    end
}

p i+1