#include <bits/stdc++.h>
using namespace std;

//高精度求和 
string num(string s1,string s2){
	string r = ""; 
	int i,len;//len存较长的长度 
	int a[250] = {0},b[250] = {0},c[250] = {0};
	//第一步：将2个字符数组逆序存入2个整数数组
	//s1 = "12345";
	for(i = 0;i < s1.size();i++){
		//0->s1.size()-1  1->s1.size()-2
		a[s1.size()-i-1] = s1[i] - '0';
	} 
	
	for(i = 0;i < s2.size();i++){
		b[s2.size()-i-1] = s2[i] - '0';
	}
	
    //第二步：逐位相加，逐位进位
    //int len = s1.size() > s2.size()?s1.size():s2.size();//三目运算符，替代if else 
	len = s1.size();
	if(s2.size() > s1.size()){
		len = s2.size();
	} 
	
	//加 
	for(i = 0;i < len;i++){
		c[i] = a[i] + b[i];
	}
	//进位
	for(i = 0;i < len;i++){
		if(c[i] >= 10){
			c[i+1] = c[i+1] + c[i] / 10;
			c[i] = c[i] % 10;
		}
	} 
	
	//第三步：逆序输出
	if(c[len] != 0){
		len++;
	} 
	
	for(i = len - 1;i>=0;i--){
		r = r + (char)(c[i] + 48);
	}
	return r;
}

int main(){
	long long m,n,x,i;
	cin>>m>>n;
	x = n - m;
	string t1,t2,t;
	t1 = "1";
	t2 = "2";
	for(i = 3;i <= x;i++){
		t = num(t1,t2);
//		cout<<i<<" "<<t<<endl;
		t1 = t2;
		t2 = t;
	}
	
	cout<<t2<<endl;
//	cout<<LONG_LONG_MAX<<endl;
    return 0;
}

/**************************************************************
	Problem: 1368
	User: admin
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2076 kb
****************************************************************/