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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <unordered_map>
#include <vector>

int main()
{
    std::string s, t;
    std::cin >> s >> t;

    std::unordered_map<char, std::vector<int>> char_pos;
    for (int i = 0; i < s.length(); i++) {
        char_pos[s[i]].push_back(i);
    }

    for (int i = 0; i < s.length(); i++) {
        char_pos[s[i]].push_back(i + s.length());
    }

    long long ans = 0;
    int ptr = 0;
    for (auto c : t) {
        if (char_pos[c].empty()) {
            std::cout << -1 << std::endl;
            return 0;
        }

        ptr = *lower_bound(char_pos[c].begin(), char_pos[c].end(), ptr) + 1;
        if (ptr >= s.length()) {
            ptr -= s.length();
            ans += s.length();
        }
    }

    ans += ptr;
    std::cout << ans << std::endl;
}