#include<bits/stdc++.h>
using namespace std;
string fib[1008]={""};
string stringadd(string a,string b)
{
    if(a.length()>b.length())
        swap(a,b);
    string ans="";
    int len1=a.length();
    int len2=b.length();
    reverse(a.begin(),a.end());
    reverse(b.begin(),b.end());
    int i,j,k,sum=0,carry=0;
    for(i=0;i<len1;i++)
    {

        sum=((a[i]-'0')+(b[i]-'0'))+carry;
        ans.push_back((sum%10)+'0');
        carry=sum/10;
    }
     for(i=len1;i<len2;i++)
    {

        sum=((b[i]-'0'))+carry;
        ans.push_back((sum%10)+'0');
        carry=sum/10;
    }
    if(carry)
        ans.push_back(carry+'0');
    reverse(ans.begin(),ans.end());
    return ans;
}
string fibo(int n)
{
    if(n==0)
        return "1";
    if(n==1)
        return "2";
    if(fib[n]!="")
        return fib[n];
        return fib[n]=stringadd(fibo(n-1),fibo(n-2));
}
int main()
{
    int n;
    while(cin>>n)
    {
        cout<<fibo(n)<<endl;
    }
    return 0;
}