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: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define all(x) (x).begin(),(x).end()
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
typedef long long ll;
const long long INF = 1LL << 60;
typedef pair<int, int> P;
int main()
{
    string S, T;
    cin >> S >> T;

    vector<vector<ll>> index(26, vector<ll>((ll)S.size(), -1));

    rep(i, S.size()) {
        index[(ll)(S[i] - 'a')][i] = i;
    }
    rep(i, 26) {
        ll place = -1;
        rep(j, S.size()) {
            if (index[i][j] != -1) {
                place = index[i][j];
                break;
            }
        }
        if (place == -1) continue;
        for (ll j = (ll)S.size() - 1; j >= 0; j--) {
            if (index[i][j] != -1) {
                place = index[i][j];
            }
            else index[i][j] = place;
        }
    }
/*
    rep(i, 26) {
        cout << "i : " << (char)('a' + i) << endl;
        rep(j, S.size()) {
            cout << index[i][j] << endl;
        }
    }*/

    ll cnt = 0, ans;
    ll now = -1;
    ll next;
    rep(i, T.size()) {
        if (now == (ll)S.size() - 1) next = index[(ll)(T[i] - 'a')][0];
        else next = index[(ll)(T[i] - 'a')][now + 1];
        if (next == -1) {
            cout << -1 << endl;
            return 0;
        }
        if (now > next) {
            cnt++;
        }
        //cout << now << " " << next << " " << cnt << endl;
        now = next;
    }

    ans = cnt * (ll)S.size();
    ans += (next + 1);

    cout << ans << endl;
    return 0;
}