#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

std::ifstream in ("nunta.in");
std::ofstream out ("nunta.out");

class largeInt
{
public:
	largeInt(unsigned long long n);
	largeInt& operator=(const unsigned long long &rhs);
	largeInt& operator+=(const largeInt &rhs);
	largeInt& operator+=(const unsigned long long &rhs);
	largeInt operator+(const largeInt &rhs) const;
	largeInt operator+(const unsigned long long &rhs) const;
	largeInt& operator-=(const largeInt &rhs);
	largeInt& operator-=(const unsigned long long &rhs);
	largeInt operator-(const largeInt &rhs) const;
	largeInt operator-(const unsigned long long &rhs) const;
	bool operator==(const largeInt &rhs) const;
	bool operator!=(const largeInt &rhs) const;
	bool operator<(const largeInt &rhs) const;
	bool operator<=(const largeInt &rhs) const;
	bool operator>(const largeInt &rhs) const;
	bool operator>=(const largeInt &rhs) const;
	friend std::ostream& operator<<(std::ostream& os, const largeInt& n);
	friend std::istream& operator>>(std::istream& is, largeInt& n);

private:
	void fixOverflow();
	void fixUnderflow();
	std::vector<int> nr;
};

largeInt::largeInt(unsigned long long n)
{
	while(n!=0)
	{
		this->nr.push_back(n%10);
		n/=10;
	}
}

largeInt& largeInt::operator=(const unsigned long long &rhs)
{
	unsigned long long n = rhs;
	while(!nr.empty())nr.pop_back();
	while(n!=0)
	{
		this->nr.push_back(n%10);
		n/=10;
	}
	return *this;
}

void largeInt::fixOverflow()
{
	for(int i = 0; i < nr.size()-1; i++)
		if(nr[i]>=10)
		{
			int aux = nr[i]%10;
			nr[i+1]=nr[i]/10;
			nr[i]=aux;
		}
	if(nr[nr.size()-1]>=10)
	{
		int i = nr.size()-1;
		while(nr[i]>=10)
		{
			nr.push_back(nr[i]%10);
			nr[i]/=10;
		}
	}
}

void largeInt::fixUnderflow()
{
	for(int i = 0; i < nr.size(); i++)
	{
		if(nr[i]<0)
		{
			nr[i+1]--;
			nr[i]+=10;
		}
	}
	while(nr.back()==0)
		nr.pop_back();
}

largeInt& largeInt::operator+=(const largeInt &rhs)
{
	if(this->nr.size()>rhs.nr.size())
	{
		for(int i = 0; i < rhs.nr.size(); i++)
			this->nr[i]+=rhs.nr[i];
	}
	else
	{
		for(int i = 0; i < this->nr.size(); i++)
			this->nr[i]+=rhs.nr[i];
		for(int i = this->nr.size(); i < rhs.nr.size(); i++)
			this->nr.push_back(rhs.nr[i]);
	}
	fixOverflow();
}

largeInt& largeInt::operator+=(const unsigned long long &rhs)
{
	largeInt aux(rhs);
	*this+=aux;
	return *this;
}

largeInt largeInt::operator+(const largeInt &rhs) const
{
	largeInt aux = *this;
	aux+=rhs;
	return aux;
}

largeInt largeInt::operator+(const unsigned long long &rhs) const
{
	largeInt aux = *this;
	aux+=rhs;
	return aux;
}

largeInt& largeInt::operator-=(const largeInt &rhs)
{
	for(int i = 0; i < rhs.nr.size(); i++)
		this->nr[i]-=rhs.nr[i];
	fixUnderflow();
	return *this;
}

bool largeInt::operator==(const largeInt &rhs) const
{
	if(this->nr.size()!=rhs.nr.size()) return false;
	else
	{
		for(int i = 0; i < rhs.nr.size(); i++)
			if(rhs.nr[i]!=this->nr[i])return false;
		return true;
	}
}

bool largeInt::operator!=(const largeInt &rhs) const
{
	return !(*this==rhs);
}

bool largeInt::operator<(const largeInt &rhs) const
{
	if(this->nr.size()<rhs.nr.size())return true;
	if(this->nr.size()>rhs.nr.size())return false;
	for(int i = rhs.nr.size()-1; i >= 1; i--)
		if(this->nr[i]>rhs.nr[i])return false;
	if(this->nr[0]>=rhs.nr[0])return false;
	return true;
}
bool largeInt::operator>=(const largeInt &rhs) const
{
	return !(*this<rhs);
}

bool largeInt::operator<=(const largeInt &rhs) const
{
	return (*this<rhs && *this==rhs);
}
bool largeInt::operator>(const largeInt &rhs) const
{
	return !(*this<=rhs);
}

std::ostream& operator<<(std::ostream& os, const largeInt& n)
{
	for(int i = n.nr.size()-1; i >= 0; i--)
		os << n.nr[i];
	return os;
}
std::istream& operator>>(std::istream& is, largeInt& n)
{
	while(!n.nr.empty())n.nr.pop_back();
	while(is.peek()>'9'&&is.peek()<'0')is.ignore();
	while(is.peek()<='9'&&is.peek()>='0')
	{
		char t;
		is >> t;
		n.nr.push_back(t-'0');
	}
	std::reverse(n.nr.begin(), n.nr.end());
	return is;
}

int main()
{
	largeInt f1(1);
	largeInt f2(1);
	int n;
	in >> n;
	for(int i = 0; i < n-1; i++)
	{
		largeInt aux(0);
		aux = f1+f2;
		f1=f2;
		f2=aux;
	}
	out << f2 << '\n';
}