First day messing with C#, don't understand error

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C#

So I'm trying to compile a code that adds up a series of variables, then provides the arithmetic mean and displays the modulo result. I've been smashing my face against a Main() error that says "CS1520 Method must have a return type" and can't figure out what I'm doing wrong. My entire code is below. I know I'm code illiterate at the moment, so please be patient with me.

What I have tried:

using System;
using System.Linq;

class Program
{
    static Main()
    {
        int number1, number2, number3;
        Console.Write("Enter an integer score");
        number1 = Convert.ToInt32(Console.ReadLine());
        Console.Write("Enter an integer score");
        number2 = Convert.ToInt32(Console.ReadLine());
        Console.Write("Enter an integer score");
        number3 = Convert.ToInt32(Console.ReadLine());

        int result = (number1 + number2 + number3) % 3;
        Console.WriteLine("The average of {0}, {1}, {2} is: {3}",
        number1, number2, number3, result);
    }
}