#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int M = 100010;
int n;
string f[M];

string J(string aa,string bb)
{
    if(aa.length()<bb.length())
    {
        string tmp=aa;
        aa=bb;
        bb=tmp;
    }
    int i,j;
    for(i=aa.length()-1,j=bb.length()-1;i>=0;i--,j--)
    {
        aa[i]=char(aa[i] + ( j >= 0 ? bb[j]-‘0‘ : 0));
        if(aa[i]-‘0‘>=10)
        {
            aa[i]=char((aa[i]-‘0‘)%10+‘0‘);
            if(i) aa[i-1]++;
            else aa=‘1‘+aa;
        }
    }
    return aa;
}

int main()
{
    int j=3;
    scanf("%d",&n);
    f[0]=‘0‘;
    f[1]=‘1‘;
    f[2]=‘2‘;
    while(j<=n)
    {
        f[j]=J(f[j-1],f[j-2]);
        j++;
    }
    cout<<f[n];
    return 0;
}