C# implementation

Author: Rafael Cunha de Almeida

Nsteps.cs

@@ -0,0 +1,27 @@
+using System;
+
+public class Nsteps {
+    public static long CoordsToNumber(long x, long y) {
+        if (y != (x-2) && y != x) {
+            return -1;
+        }
+        if (x % 2 == 0) {
+            return x + y;
+        } else {
+            return x + y - 1;
+        }
+    }
+
+    public static void Main() {
+        int lines = Convert.ToInt32(Console.ReadLine());
+        while (lines-- > 0) {
+            string[] tuple = Console.ReadLine().Split(' ');
+            long number = CoordsToNumber(Convert.ToInt64(tuple[0]), Convert.ToInt64(tuple[1]));
+            if (number < 0)  {
+                Console.WriteLine("No Number");
+            } else {
+                Console.WriteLine(number);
+            }
+        }
+    }
+}

nsteps.test

@@ -0,0 +1,4 @@
+3
+4 2
+6 6
+3 4