diff --git a/04-fibonacci/index.js b/04-fibonacci/index.js
index 37c64cc..96c8368 100644
--- a/04-fibonacci/index.js
+++ b/04-fibonacci/index.js
@@ -1,4 +1,15 @@
 export function fibonacci(value) {
-  // implementar logica aqui
+  let beforeLastNumber = 0;
+  let lastNumber = 1;
+  let nextNumber;
   
+  if (value < 2) return value;
+
+  for (let i = 2; i <= value; i++) {
+    nextNumber = lastNumber + beforeLastNumber;
+    beforeLastNumber = lastNumber;
+    lastNumber = nextNumber;
+  }
+
+  return lastNumber;
 }
\ No newline at end of file