PROJECT EULER #40

Link to Project Euler problem 40

An irrational decimal fraction is created by concatenating the positive integers:

0.123456789101112131415161718192021...

It can be seen that the 12^th digit of the fractional part is 1.

If d_n represents the n^th digit of the fractional part, find the value of the following expression.

d₁ x d₁₀ x d₁₀₀ x d₁₀₀₀ x d₁₀₀₀₀ x d₁₀₀₀₀₀ x d_1000000

using System;
using System.Text;

namespace project_euler
{
class Program
{
  static void Main()
  {
      //Problem 40
      DateTime start = DateTime.Now;
      StringBuilder sb = new StringBuilder();
      for (int i = 1; i < 200000; i++)
              sb.Append(i.ToString());
      string s = sb.ToString();
      long sum = int.Parse(s[0].ToString())*int.Parse(s[9].ToString())*int.Parse(s[99].ToString())*int.Parse(s[999].ToString())*int.Parse(s[9999].ToString())*int.Parse(s[99999].ToString())*int.Parse(s[999999].ToString());
      Console.WriteLine(sum);
      TimeSpan time = DateTime.Now - start;
      Console.WriteLine("This took {0}", time);
      Console.ReadKey();
  }
}
}