Finished

src/AssessmentPartOne.java

@@ -44,8 +44,16 @@ public class AssessmentPartOne {
 		
 		int sumOfSquares = 0;
 		
+		if (start < 0 || end < 0 || end - start < 2) { //catches invalid inputs (negative start or end values and no values in between)
+			return -1;
+		} else {
+			for (int i = 1; i < end - start; i++) { //iterates through numbers between
+				sumOfSquares += (start + i); //adds value to the running total
+			}
+			return sumOfSquares;
+		}
+		
 		
-		return sumOfSquares;
 	}
 	
 }