diff --git a/lib/fib.ts b/lib/fib.ts
new file mode 100644
index 0000000..4ae053a
--- /dev/null
+++ b/lib/fib.ts
@@ -0,0 +1,16 @@
+// https://github.com/yangzj1992/FE-Questions/blob/master/codewars/5541f58a944b85ce6d00006a.Product%20of%20consecutive%20Fib%20numbers/Product%20of%20consecutive%20Fib%20numbers.md
+export function fib(prod: number) {
+  let n = 0;
+  let nPlus = 1;
+
+  while (n * nPlus < prod) {
+    nPlus = n + nPlus;
+    n = nPlus - n;
+  }
+
+  return [n, nPlus, n * nPlus === prod];
+}
+
+// console.log(fib(55), [21, 34, true]);
+console.log(fib(714), [21, 34, true]);
+// console.log(fib(800), [34, 55, false]);