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: Wrong Answer)


using System.Collections;
using System.Text;
using System.Threading.Tasks;
using static System.Math;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System;
using System.Numerics;


class Program
{

    static void Main()
    {
        #region 入力
        string s = ReadStr;
        string t = ReadStr;
        #endregion

        Dictionary<char, List<int>> sMap = new Dictionary<char, List<int>>();
        for (int i = 0; i < s.Length; i++)
        {
            if (sMap.ContainsKey(s[i])) sMap[s[i]].Add(i);
            else sMap.Add(s[i], new List<int>() { i});
        }

        long current = -1;
        long ans = 0;
        for (int i = 0; i < t.Length; i++)
        {
            if (sMap.ContainsKey(t[i]))
            {
                Vector2Int v = BinarySearch(sMap[t[i]], n => n < current);
                if (v.Y == sMap[t[i]].Count)
                {
                    ans += s.Length;
                    current = sMap[t[i]][0];
                }
                else current = sMap[t[i]][v.Y];
            }
            else
            {
                WriteLine(-1);
                ReadLine();
                return;
            }
        }

        WriteLine(ans+current+1);
        ReadLine();
    }


    static Vector2Int BinarySearch(List<int> numbers,Func<int,bool> judge)
    {
        int max = numbers.Count;
        int min = -1;
        int mid = (min + max) / 2;

        while (max-min>1)
        {
            if (judge(numbers[mid]))
            {
                min = mid;
                mid = (mid + max) / 2;
            }
            else
            {
                max = mid;
                mid = (mid + max) / 2;
            }
        }

        if (max == numbers.Count) return new Vector2Int(mid, mid + 1);
        else if (min==-1) return new Vector2Int(-1, 0);
        else
        {
            return judge(numbers[mid]) != judge(numbers[mid + 1]) ? new Vector2Int(mid, mid + 1)
            : new Vector2Int(mid - 1, mid);
        }
    }

    struct Vector2Int
    {
        public Vector2Int(int x, int y)
        {
            X = x;
            Y = y;
        }
        public int X;
        public int Y;
        public double Magnitude => Math.Sqrt(X * X + Y * Y);

        public static Vector2Int zero => new Vector2Int(0, 0);
        public static Vector2Int u => new Vector2Int(0, 1);
        public static Vector2Int r => new Vector2Int(1, 0);
        public static Vector2Int d => new Vector2Int(0, -1);
        public static Vector2Int l => new Vector2Int(-1, 0);
        public static Vector2Int[] AllDirections => new Vector2Int[4] { u, r, d, l };

        public static Vector2Int operator +(Vector2Int a, Vector2Int b)
        {
            return new Vector2Int(a.X + b.X, a.Y + b.Y);
        }
        public static Vector2Int operator -(Vector2Int a, Vector2Int b)
        {
            return new Vector2Int(a.X - b.X, a.Y - b.Y);
        }
        public static bool operator ==(Vector2Int a, Vector2Int b)
        {
            return a.X == b.X && a.Y == b.Y;
        }
        public static bool operator !=(Vector2Int a, Vector2Int b)
        {
            return a.X != b.X || a.Y != b.Y;
        }
        public static Vector2Int operator *(Vector2Int v, int n)
        {
            return new Vector2Int(v.X * n, v.Y * n);
        }
        public static Vector2Int operator *(int n, Vector2Int v)
        {
            return new Vector2Int(v.X * n, v.Y * n);
        }
    }
    struct Vector3Int
    {
        public Vector3Int(int x, int y, int z)
        {
            X = x;
            Y = y;
            Z = z;
        }
        public int X;
        public int Y;
        public int Z;

        public double Magnitude => Math.Sqrt(X * X + Y * Y + Z * Z);

        public static Vector3Int zero => new Vector3Int(0, 0, 0);
        public static Vector3Int u => new Vector3Int(0, 1, 0);
        public static Vector3Int r => new Vector3Int(1, 0, 0);
        public static Vector3Int d => new Vector3Int(0, -1, 0);
        public static Vector3Int l => new Vector3Int(-1, 0, 0);

        public static Vector3Int operator +(Vector3Int a, Vector3Int b)
        {
            return new Vector3Int(a.X + b.X, a.Y + b.Y, a.Z + b.Z);
        }
        public static Vector3Int operator -(Vector3Int a, Vector3Int b)
        {
            return new Vector3Int(a.X - b.X, a.Y - b.Y, a.Z - b.Z);
        }
        public static bool operator ==(Vector3Int a, Vector3Int b)
        {
            return a.X == b.X && a.Y == b.Y && a.Z == b.Z;
        }
        public static bool operator !=(Vector3Int a, Vector3Int b)
        {
            return a.X != b.X || a.Y != b.Y || a.Z != b.Z;
        }
        public static Vector3Int operator *(Vector3Int v, int n)
        {
            return new Vector3Int(v.X * n, v.Y * n, v.Z * n);
        }
        public static Vector3Int operator *(int n, Vector3Int v)
        {
            return new Vector3Int(v.X * n, v.Y * n, v.Z * n);
        }
    }

    #region Reader
    static Vector2Int ReVec2Int { get {
            string[] s = Console.ReadLine().Split(' ');
            return new Vector2Int(int.Parse(s[0]), int.Parse(s[1]));
        } }
    static Vector2Int[] ReadVec2Ints(int n)
    {
        List<Vector2Int> list = new List<Vector2Int>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadInts;
            list.Add(new Vector2Int(ab[0], ab[1]));
        }
        return list.ToArray();
    }
    static HashSet<Vector2Int> ReadVec2IntHash(int n)
    {
        HashSet<Vector2Int> hash = new HashSet<Vector2Int>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadInts;
            hash.Add(new Vector2Int(ab[0], ab[1]));
        }
        return hash;
    }
    static string ReadStr => Console.ReadLine();
    static string[] ReadStrs => Console.ReadLine().Split(' ');
    static int ReadInt => Convert.ToInt32(Console.ReadLine());
    static int[] ReadInts => Console.ReadLine().Split(' ').Select(s => Convert.ToInt32(s)).ToArray();
    static long ReLong => Convert.ToInt64(Console.ReadLine());
    static long[] ReadLongs => Console.ReadLine().Split(' ').Select(s => Convert.ToInt64(s)).ToArray();
    static long[,] ReLongMatrix(int r, int c)
    {
        var mat = new long[r, c];
        for (int i = 0; i < r; ++i)
        {
            var x = ReadLongs;
            for (int j = 0; j < c; ++j)
            {
                mat[i, j] = x[j];
            }
        }
        return mat;
    }
    static Tuple<string, string>[] ReTupleStr(int n)
    {
        List<Tuple<string, string>> list = new List<Tuple<string, string>>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadStrs;
            list.Add(new Tuple<string, string>(ab[0], ab[1]));
        }
        return list.ToArray();
    }
    static Tuple<long, long>[] ReTupleLong(int n)
    {
        List<Tuple<long, long>> list = new List<Tuple<long, long>>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadLongs;
            list.Add(new Tuple<long, long>(ab[0], ab[1]));
        }
        return list.ToArray();
    }
    static Tuple<int, int>[] ReTupleInt(int n)
    {
        List<Tuple<int, int>> list = new List<Tuple<int, int>>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadInts;
            list.Add(new Tuple<int, int>(ab[0], ab[1]));
        }
        return list.ToArray();
    }
    static Tuple<double, double>[] ReTupleDouble(int n)
    {
        List<Tuple<double, double>> list = new List<Tuple<double, double>>();
        for (int i = 0; i < n; ++i)
        {
            var ab = ReadLongs;
            list.Add(new Tuple<double, double>(ab[0], ab[1]));
        }
        return list.ToArray();
    }
    static Dictionary<int, HashSet<int>> ReAdjacencyList(int N, int M)
    {
        Dictionary<int, HashSet<int>> dict = new Dictionary<int, HashSet<int>>();
        for (int i = 0; i <= N; ++i)
        {
            dict.Add(i, new HashSet<int>());
        }
        for (int i = 0; i < M; ++i)
        {
            var ab = ReadInts;
            dict[ab[0]].Add(ab[1]);
            dict[ab[1]].Add(ab[0]);
        }
        return dict;
    }
    #endregion
}