using namespace std;
#include <fstream>
ifstream fin("kfib.in");
ofstream fout ("kfib.out");
int main ()
{ int k,t1,t2,i,T;
fin>>k;
t1=1;
t2=1;
for(i=3;i<=k;i++)
{	T=t1+t2;
    t1=t2;
	t2=T;
}
fout<<T;
return 0;
}