Enter the month and date to get the first day of the year

Console.WriteLine ("Please enter a few months and the number of days for you to figure out the day of the Year");
int m1 = to, M2 = 31, M3 = To, M4 =, M5 = To, M6 =, M7 = to, M8 = to, M9 =, M10 =, M11 =--M12
Console.Write ("Please enter the month:");
int m = Convert.ToInt32 (Console.ReadLine ());
Console.Write ("Please enter the date:");
int d = Convert.ToInt32 (Console.ReadLine ());
if (d >= 1 && d <= 31)
{

Switch (m)
{
Case 1:
Console.WriteLine ("This year's {0}", D, "Day");
Break

Case 2:
Console.WriteLine ("This year's {0}", M1 + D, "Day");
Break

Case 3:
Console.WriteLine ("This year's {0}", M1 + m2 + D, "Day");
Break

Case 4:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + D, "Day");
Break

Case 5:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + m4 + D, "Day");
Break

Case 6:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + m5 + D, "Day");
Break

Case 7:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + D, "Day");
Break
Case 8:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + M7 + D, "Day");
Break

Case 9:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + M7 + m8 + D, "Day");
Break

Case 10:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + M7 + m8 + M9 + D, "Day");
Break

Case 11:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + M7 + m8 + M9 + M10 + D, "Day");
Break

Case 12:
Console.WriteLine ("This year's {0}", M1 + m2 + m3 + M4 + M5 + M6 + M7 + m8 + M9 + M10 + M11 + D, "Day");
Break
Default

Console.WriteLine ("Entered month error");
Break

}
}
Else
{
Console.WriteLine ("The date entered is incorrect. ");
}

Enter the month and date to get the first day of the year