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 <bits/stdc++.h>

std::vector<std::array<int, 26>> subsequenceAutomaton(const std::string& S, const char initial_char = 'a')
{
	std::vector<std::array<int, 26>> table(S.size() + 2);
	std::fill(table.back().begin(), table.back().end(), (int)table.size() - 1);
	table[table.size() - 2] = table.back();

	for (int s_i{(int)S.size() - 1}; s_i >= 0; s_i--)
	{
		std::copy(table[s_i + 1].begin(), table[s_i + 1].end(), table[s_i].begin());
		table[s_i][S[s_i] - initial_char] = s_i + 1;
	}
	return std::move(table);
}

int64_t solve();

int main()
{
	printf("%lld\n", solve());

	return 0;
}

int64_t solve()
{
	std::string s, t;
	std::cin >> s >> t;
	auto table{subsequenceAutomaton(s)};
	int now{};
	int64_t ans{};
	for (char& e: t)
	{
		int next{table[now][e - 'a']};
		if (next == (int)table.size() - 1)
		{
			ans += (int)s.size();
			next = table[0][e - 'a'];
		}
		if (next == (int)table.size() - 1)
			return -1ll;
		now = next;
	}
	ans += now;
	return ans;
}