// main.cpp
// 1064
//
// Created by jy zhou on 26/06/13.
// Copyright (c) 2013年 jy zhou. All rights reserved.
//
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cstring>
#include <limits>
#include <cmath>
#include <algorithm>
const int DIGITAL_CAPACITY=10;
const int MAX_LENGTH=1000;
using namespace std;
class high_precision
{
private:
int num[MAX_LENGTH],length;
public:
high_precision()
{
memset(num, 0, sizeof(num));
length = 0;
};
high_precision(int initial_num)
{
memset(num, 0, sizeof(num));
length = log10(initial_num);
for (int i=0; initial_num>0; initial_num/=DIGITAL_CAPACITY) {
num[i] = initial_num % DIGITAL_CAPACITY;
i++;
}
};
void add(const high_precision &adder)
{
for (int i=0;i<max(length,adder.length);i++)
{
num[i] += adder.num[i];
}
update();
}
void update()
{
int i;
for (i=0; num[i]>=DIGITAL_CAPACITY; i++) {
num[i+1] += num[i] / DIGITAL_CAPACITY;
num[i] %= DIGITAL_CAPACITY;
}
length = max(i, length);
}
void print()
{
for (int i=length-1; i>=0; i--) {
putchar(48+num[i]);
}
}
};
int main()
{
int n;
high_precision a(1),b(1);
cin>>n;
for (int i=2;i<n;i++)
{
if (i%2=0) a.add(b);
else b.add(a);
}
if (n%2 = 0) a.print;
else b.print;
return 0;
}