#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    long long int n,f1=0,f2=1,f3=0,cont=1,result;

    ifstream in("kfib.in");
    ofstream out("kfib.out");

    in>>n;
    in.close();

    if(n==1)
    {
        result=f2;
    }
    else
    {
         while(cont<n)
        {

        f3=f1+f2;
        f1=f2;
        f2=f3;

        cont=cont+1;
        }

        result=f3;
    }
    out<<result;
    out.close();
    return 0;
}