FibonacciIteration.java

import java.io.*;
import java.math.*;
import java.util.*;

public class Solution {

    private static BigInteger fibonacci(BigInteger count){
           if(count.compareTo(BigInteger.ZERO) <= 0){
               return BigInteger.ZERO;
           }else if(count.compareTo(BigInteger.ONE) == 0){
               return BigInteger.ONE;
           }
           BigInteger previous=BigInteger.ZERO;
           BigInteger current=BigInteger.ONE;
           BigInteger next=BigInteger.ZERO;
           for(int i=0 ; i<=count.intValue() ; i++){
               previous = current;
               current = next;
               next = previous.add(current);
           }
           return current;
    }
    
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNextInt()){
            int n = scanner.nextInt();
            System.out.println(fibonacci(BigInteger.valueOf(n)));
        }
    }
}