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 Python (3.4.3) (judge verdict: Accepted)

import bisect
from collections import defaultdict
import sys
sys.setrecursionlimit(10**9)
input = sys.stdin.readline

S = input()[:-1]
T = input()[:-1]

# 作れない場合
if any(t not in S for t in T):
    print(-1)
    exit()


D = defaultdict(lambda: [])
min_D = defaultdict(lambda: len(S)+1)
for i, s in enumerate(S):
    D[s].append(i)
    min_D[s] = min(i, min_D[s])

for s in D.keys():
    D[s] = sorted(D[s])

cur_pos = 0
repeat = 0
for t in T:
    #print("cur->", cur_pos)
    ind = bisect.bisect_left(D[t], cur_pos)
    if ind >= len(D[t]):
        repeat += 1
        cur_pos = min_D[t]+1
    else:
        cur_pos = D[t][ind]+1

print(len(S)*repeat+cur_pos)