CF91A.Newspaper Headline

A newspaper is published in Walrusland. Its heading is _s_1, it consists of lowercase Latin letters. Fangy the little walrus wants to buy several such newspapers, cut out their headings, glue them one to another in order to get one big string. After that walrus erase several letters from this string in order to get a new word _s_2. It is considered that when Fangy erases some letter, there's no whitespace formed instead of the letter. That is, the string remains unbroken and it still only consists of lowercase Latin letters.

For example, the heading is "abc". If we take two such headings and glue them one to the other one, we get "abcabc". If we erase the letters on positions 1 and 5, we get a word "bcac".

Which least number of newspaper headings _s_1 will Fangy need to glue them, erase several letters and get word _s_2?

《海象国日报》的报头为字符串 $s_1$，仅由小写拉丁字母组成。小海象 Fangy 想购买若干份该报纸，剪下每份报纸的报头，再将这些报头按顺序首尾粘贴，从而得到一个长字符串。随后，Fangy 从该长字符串中擦除若干个字母，得到一个新的单词 $s_2$。注意：当 Fangy 擦除某个字母时，该位置不会产生空格，即字符串保持连续，且仍仅由小写拉丁字母组成。

例如，报头为 "abc"。若取两份该报头并粘贴在一起，得到 "abcabc"；若擦除位置 $1$ 和 $5$（从 $0$ 开始计数）上的字母，则得到单词 "bcac"。

问：Fangy 至少需要多少份报纸（即至少需要多少个 $s_1$）进行粘贴和擦除操作，才能得到单词 $s_2$？

The input data contain two lines. The first line contain the heading _s_1, the second line contains the word _s_2. The lines only consist of lowercase Latin letters (1 ≤ |_s_1| ≤ 104, 1 ≤ |_s_2| ≤ 106).

输入数据包含两行。第一行包含标题 $s_1$，第二行包含单词 $s_2$。每行仅由小写拉丁字母组成（$1 \le |s_1| \le 10^4$，$1 \le |s_2| \le 10^6$）。

If it is impossible to get the word _s_2 in the above-described manner, print "-1" (without the quotes). Otherwise, print the least number of newspaper headings _s_1, which Fangy will need to receive the word _s_2.

如果无法通过上述方式得到字符串 $s_2$，则输出 -1（不带引号）。否则，输出 Fangy 为得到字符串 $s_2$ 所需的最少报纸标题数 $s_1$。