Problem:
Score : 200 points

Problem Statement

Takahashi's house has only one socket.

Takahashi wants to extend it with some number of power strips, each with A sockets, into B or more empty sockets.

One power strip with A sockets can extend one empty socket into A empty sockets.

Find the minimum number of power strips required.

Constraints

All values in input are integers.

2 \leq A \leq 20

1 \leq B \leq 20

Input

Input is given from Standard Input in the following format:

A B

Output

Print the minimum number of power strips required.

Sample Input 1

4 10

Sample Output 1

3

3 power strips, each with 4 sockets, extend the socket into 10 empty sockets.

Sample Input 2

8 9

Sample Output 2

2

2 power strips, each with 8 sockets, extend the socket into 15 empty sockets.

Sample Input 3

8 8

Sample Output 3

1

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
//using ProCon.Util;

namespace ProCon
{
    class Program
    {
        static void Main(string[] args)
        {
            AC139B();
        }

        static void AC139B()
        {
            //https://atcoder.jp/contests/abc139/tasks
            
            var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
            var a = input[0];   //a口の電源タップ
            var b = input[1];   //B口以上の未使用口
            
            var x = 0;  //必要な電源タップの個数
            if (a > b)
            {
                x = 1;
            }
            else
            {
                x = (b - a) % (a - 1) == 0 ? (b - a) / (a - 1) + 1 : (b - a) / (a - 1) + 2;
            }
            Console.WriteLine(x);
        }

    }
}