Problem:
Score : 400 points

Problem Statement

Snuke has one biscuit and zero Japanese yen (the currency) in his pocket.
He will perform the following operations exactly K times in total, in the order he likes:

Hit his pocket, which magically increases the number of biscuits by one.

Exchange A biscuits to 1 yen.

Exchange 1 yen to B biscuits.

Find the maximum possible number of biscuits in Snuke's pocket after K operations.

Constraints

1 \leq K,A,B \leq 10^9

K,A and B are integers.

Input

Input is given from Standard Input in the following format:

K A B

Output

Print the maximum possible number of biscuits in Snuke's pocket after K operations.

Sample Input 1

4 2 6

Sample Output 1

7

The number of biscuits in Snuke's pocket after K operations is maximized as follows:

Hit his pocket. Now he has 2 biscuits and 0 yen.

Exchange 2 biscuits to 1 yen. his pocket. Now he has 0 biscuits and 1 yen.

Hit his pocket. Now he has 1 biscuits and 1 yen.

Exchange 1 yen to 6 biscuits. his pocket. Now he has 7 biscuits and 0 yen.

Sample Input 2

7 3 4

Sample Output 2

8

Sample Input 3

314159265 35897932 384626433

Sample Output 3

48518828981938099

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

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

namespace ProconTemplate
{
    class Doing
    {
        public static long bisToMoney = 0;
        public static long moneyToBis = 0;

        public static void Main(string[] args)
        {
            var inputInt = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();
            
            if(inputInt[0] <= inputInt[1])
            {
                Console.WriteLine(inputInt[0] + 1);
                return;
            }

            if(inputInt[1]+2 >= inputInt[2])
            {
                Console.WriteLine(inputInt[0] + 1);
                return;
            }

            // Calc
            var remaining = inputInt[0] - (inputInt[1] + 1);
            var bis = inputInt[2] + ((remaining / 2) * (inputInt[2] - inputInt[1]));
            if((remaining % 2) == 1) { bis = bis + 1; }
            Console.WriteLine(bis);
        }
    }
}