class Solution{

 public:

     /**

      * @param n: an integer

      * @return an integer f(n)

      */

     int fibonacci(int n) {

         // write your code here

         int a=,b=;

         for (int i=; i<n; i++) {

             a = a+b;

             b = a-b;

         }

         return a;

     }

 };