using System;

public class Test
{
	public static void Main()
	{
		string stringNumber = "-42";
		int number = StringToInteger(stringNumber);
		
		System.Console.WriteLine(number);
	}
	
	public static int StringToInteger(string value)
    {
        bool negative = false;
        int i = 0;

        if (value[0] == '-')
        {
            negative = true;
            ++i;
        }

        int number = 0;
        for (; i < value.Length; ++i)
        {
            var character = value[i];
            number = (number << 1) + (number << 3) + (character - '0');
        }

        if (negative)
            number = -number;
        return number;
    }
}