from ast import main
import sys


def task(s, t):
    if len(s) < len(t):
        return -1
    need_count = 0
    for a in set(t):
        if s.count(a) >= t.count(a):
            continue
        need_count += abs(s.count(a)-t.count(a))
    need_count += (len(s)-len(t))
    return need_count

s = input()
t = input()
print(task(s, t))