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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;

namespace Algorithm
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Console.ReadLine();
            var t = Console .ReadLine();
            var dict = new Dictionary<char, List<int>>();
            for (var i = 0; i < s.Length; i++) {
               if (dict.ContainsKey(s[i]))
                   dict[s[i]].Add(i+1);
               else
               {
                  dict[s[i]] = new List<int>();
                  dict[s[i]].Add(i+1);
               }
            }

            var ans = 0L;
            var bef = 0;
            for (var i = 0; i < t.Length; i++) {
                if (!dict.ContainsKey(t[i])) {
                   Console.WriteLine(-1);
                   return;
                } else {
                   var list = dict[t[i]];
                   var cur = UpperBound(list, bef);
                   if (cur < list.Count) {
                      ans += list[cur] - bef;
                      bef = list[cur];
                   } else {
                      ans += s.Length - bef + list[0];
                      bef = list[0];
                   }
                   //Console.WriteLine(ans);
                }
            }
            
            Console.WriteLine(ans);
        }

        public static int UpperBound(List<int> arr, int start, int end, int value, IComparer<int> comparer)
        {
            int low = start;
            int high = end;
            int mid;
            while (low < high)
            {
                mid = ((high - low) >> 1) + low;
                if (comparer.Compare(arr[mid], value) <= 0)
                    low = mid + 1;
                else
                    high = mid;
            }
            return low;
        }

        public static int UpperBound(List<int> arr, int value)
        {
            return UpperBound(arr, 0, arr.Count, value, Comparer<int>.Default);
        }
    }
}