package question;

public class Question509 {
 public int fib(int n) {
 if (n==0 || n==1) return n;
 int x=0;
 int y=1;
 for (int i = 2; i <= n; i++) {
 int t=x+y;
 x=y;
 y=t;
 }
 return y;
 }
}