cs num Binary to Decimal Number System

using System;

class BinarytoDecimal
{
    static void Main()
    {
        char[] chars = Console.ReadLine().ToCharArray();
        long sum = 0;

        for (int i = (chars.Length-1); i >= 0 ; i-- )
            if (chars[i] == '1')
                sum += (long)Math.Pow(2, ((chars.Length-1)-i));

        Console.WriteLine(sum);
    }
}