[Init] Solved solutions

cs/478A.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace _478A
+{
+	class Program
+	{
+		static void Main(string[] args)
+		{
+			int[] a = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
+			int sum = 0;
+			for (int i = 0; i < 5; i++)
+			{
+				sum += a[i];
+			}
+			Console.WriteLine((sum % 5 == 0 && sum != 0) ? sum / 5 : -1);
+		}
+	}
+}