September Morn Update

Task/Fibonacci-sequence/BASIC/fibonacci-sequence-5.basic

@@ -1,8 +1,14 @@
-10 INPUT "ENTER VALUE OF N"; N
-20 N1 = 0 : N2 = 1
-30 FOR K=1 TO N
-40   SUM = N1+N2
-50   N1 = N2
-60   N2 = SUM
-70 NEXT K
-80 PRINT N1
+FUNCTION itFib (n)
+    n1 = 0
+    n2 = 1
+    FOR k = 1 TO ABS(n)
+        sum = n1 + n2
+        n1 = n2
+        n2 = sum
+    NEXT k
+    IF n < 0 THEN
+        itFib = n1 * ((-1) ^ ((-n) + 1))
+    ELSE
+        itFib = n1
+    END IF
+END FUNCTION