[Init] Solved solutions

cs/546A.cs

@@ -0,0 +1,13 @@
+using System;
+
+namespace _546A
+{
+	class Program
+	{
+		static void Main(string[] args)
+		{
+			int[] a = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
+			Console.WriteLine("{0}", Math.Max(a[0] * a[2] * (a[2] + 1) / 2 - a[1], 0));
+		}
+	}
+}