diff --git a/e3/e3.cs b/e3/e3.cs
new file mode 100644
index 0000000..0d891cc
--- /dev/null
+++ b/e3/e3.cs
@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+public class E3 {
+	public static List<long> factor(long n) {
+		for (long i = 2; i < Math.Sqrt(n); i++) {
+			if (n % i == 0) {
+				return factor(n/i).Concat(factor(i)).ToList();
+			}
+		}
+		return new List<long> {n};
+	}
+
+	public static void Main() {
+		
+		System.Console.WriteLine(factor(600851475143).Max());
+	}
+}
+
+