using namespace std;
#include <cstdio>
int main()
{
	freopen("kfib.in","r",stdin);
	freopen("kfib.out","w",stdout);
int n,n1,n2,n3,d;
scanf("%l",&n);
n1=1;
n2=1;
n3=1;
for(d=3;d<=n;d++)
{
n3=n1+n2;
n1=n2;
n2=n3;
}
printf("%l",n3);
return 0;
}