#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<map>
#include<iostream>
using namespace std;
#define ll long double
const int L=1005;
ll c[233][233];

int compare(string str1,string str2)
{
    if(str1.length()>str2.length()) return 1;
    else if(str1.length()<str2.length())  return -1;
    else return str1.compare(str2);
}
//高精度加法
//只能是两个正数相加
string add(string str1,string str2)//高精度加法
{
    string str;

    int len1=str1.length();
    int len2=str2.length();
    //前面补0，弄成长度相同
    if(len1<len2)
    {
        for(int i=1;i<=len2-len1;i++)
           str1="0"+str1;
    }
    else
    {
        for(int i=1;i<=len1-len2;i++)
           str2="0"+str2;
    }
    len1=str1.length();
    int cf=0;
    int temp;
    for(int i=len1-1;i>=0;i--)
    {
        temp=str1[i]-'0'+str2[i]-'0'+cf;
        cf=temp/10;
        temp%=10;
        str=char(temp+'0')+str;
    }
    if(cf!=0)  str=char(cf+'0')+str;
    return str;
}


string num[222];

int main () {

    int n;
    while(~scanf("%d", &n)) {
        num[1] = "1";
        num[2] = "2";
        for(int i = 3; i <= n; i++) {
            num[i] = add(num[i - 1], num[i - 2]);
        }
        cout << num[n] << endl;
    }
}