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 <vector>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <set>
#define REP(i, n) for (int i = 0; i < (n); ++i)
using namespace std;
using ll = long long;
using arr = vector<ll>;
constexpr ll MOD = 1000000007;
constexpr ll INF = 1LL << 60;
constexpr int MAX = 2020;

string s, t;
set<int> st[26];

int main()
{
  cin >> s >> t;
  int n = (int)s.size();
  int m = (int)t.size();
  s += s;


  for(int i = 0; i < n * 2; ++i) {
    st[s[i] - 'a'].insert(i);
  }

  ll ans = 0, pos = 0;
  for(int i = 0; i < m; ++i) {
    if (st[t[i] - 'a'].empty()) {
      cout << -1;
      return 0;
    }
    int next = *st[t[i] - 'a'].lower_bound(pos) + 1;
    ans += next - pos;
    pos = next % n;
  }
  cout << ans;
  return 0;
}