/g/ for mike in c#

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

namespace ConsoleApplication3 {
    class Program {
        static void Main(string[] args) {
            Console.WriteLine("Please enter a letter grade.");
            Console.Write(">>>");
            var letterGrade = Console.ReadLine();
            Dictionary<string, double> gradeConversion =
                new Dictionary<string, double>()
            {
                {"A", 4.0},
                {"B", 3.0},
                {"C", 2.0},
                {"D", 1.0},
                {"F", 0.0}
            };
            Dictionary<string, double> signs =
                new Dictionary<string, double>()
            {
                {"+", 0.3},
                {"-", -0.3},
            };
            if (letterGrade.Length == 1) {
                Console.WriteLine(gradeConversion[letterGrade]);
            }
            else if (letterGrade.Length == 2) {
                double tempGrade = gradeConversion[letterGrade[0].ToString()];
                tempGrade += signs[letterGrade[1].ToString()];
                Console.WriteLine(tempGrade);
            }
            else {
                Console.WriteLine("YOU HAVE FUCKED UP NOW");
            }
            Console.WriteLine("Press any key to exit.");
            Console.ReadLine();
        }
    }
}