Problem:
Score : 500 points

Problem Statement

Given are two strings s and t consisting of lowercase English letters. Determine if there exists an integer i satisfying the following condition, and find the minimum such i if it exists.

Let s' be the concatenation of 10^{100} copies of s. t is a subsequence of the string {s'}_1{s'}_2\ldots{s'}_i (the first i characters in s').

Notes

A subsequence of a string a is a string obtained by deleting zero or more characters from a and concatenating the remaining characters without changing the relative order. For example, the subsequences of contest include net, c, and contest.

Constraints

1 \leq |s| \leq 10^5

1 \leq |t| \leq 10^5

s and t consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

s
t

Output

If there exists an integer i satisfying the following condition, print the minimum such i; otherwise, print -1.

Sample Input 1

contest
son

Sample Output 1

10

t = son is a subsequence of the string contestcon (the first 10 characters in s' = contestcontestcontest...), so i = 10 satisfies the condition.

On the other hand, t is not a subsequence of the string contestco (the first 9 characters in s'), so i = 9 does not satisfy the condition.

Similarly, any integer less than 9 does not satisfy the condition, either. Thus, the minimum integer i satisfying the condition is 10.

Sample Input 2

contest
programming

Sample Output 2

-1

t = programming is not a substring of s' = contestcontestcontest.... Thus, there is no integer i satisfying the condition.

Sample Input 3

contest
sentence

Sample Output 3

33

Note that the answer may not fit into a 32-bit integer type, though we cannot put such a case here.

Solution in PyPy3 (7.3.0) (judge verdict: Accepted)

from bisect import bisect_left, bisect_right
s = input()
t = input()
n_s = len(s)
n_t = len(t)


idx = [[] for _ in range(26)]
#print(ord("a"))
#print(ord("z"))

def a_idx(a):
    idx = ord(a)
    idx -= 97
    return idx


for i in range(n_s):
    idx[a_idx(s[i])].append(i)

t_syutugenkasyo = []
for i in range(n_t):
    t_syutugenkasyo.append(idx[a_idx(t[i])])
#print(t_syutugenkasyo)

now = -1
ans = 0
for i in range(n_t):
    if len(t_syutugenkasyo[i]) == 0:
        print(-1)
        exit()
    ni = bisect_right(t_syutugenkasyo[i], now)
    if ni >= len(t_syutugenkasyo[i]):
        ans += n_s
        now = -1
        ni = bisect_right(t_syutugenkasyo[i], now)
        now = t_syutugenkasyo[i][ni]
    else:
        now = t_syutugenkasyo[i][ni]
ans += now+1
print(ans)