#include<fstream>

using namespace std;

int main()
{
    unsigned int t,i,t1,t2,k;
    ifstream f("kfib.in");
    ofstream g("kfib.out");
    f>>k;
    i=1;
    t1=0;
    t2=1;
    while(i>k)
    {t1=t2;
    t2=t;
    t=t1+t2;
    i++;
    }
    g<<t;
    f.close();
    g.close();
    return 0;
}