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package stackandqueues;

import java.math.BigInteger;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Scanner;

/**
 *
 * @author kalin
 */
public class O8_StackAndQueues {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String input = scanner.nextLine();
        int nFibonacci = Integer.parseInt(input);

        System.out.println(getFibonacci(nFibonacci, new BigInteger[nFibonacci + 1]));

    }

    private static BigInteger getFibonacci(int nFibonacci,BigInteger[] fibonacciNumber) {

        if (nFibonacci == 0 || nFibonacci == 1) {
            return BigInteger.valueOf(1);

        }
        BigInteger  temp = fibonacciNumber[nFibonacci];
        if (temp == BigInteger.ZERO || temp == null) {
            temp = getFibonacci(nFibonacci - 2, fibonacciNumber).add(getFibonacci(nFibonacci - 1, fibonacciNumber));
            fibonacciNumber[nFibonacci] = temp;
        }

        return temp;
    }

}