#include<fstream>
using namespace std;
ifstream f("nunta.in");
ofstream g("nunta.out");
int i,j,t,n,a[1000],b[1000];
int main()
{f>>n;
 a[0]=1;
 b[0]=1;
 a[1]=1;
 b[1]=2;
 for(j=1;j<n/2.;++j){t=0;
                     i=1;
					 while(i<=a[0]||i<=b[0]||t>0){t=t+a[i]+b[i];
					                              a[i]=t%10;
					                              t/=10;
												  ++i;
												 }
					 a[0]=i-1;
					 t=0;
                     i=1;
					 while(i<=a[0]||i<=b[0]||t>0){t=t+a[i]+b[i];
					                              b[i]=t%10;
					                              t/=10;
						 						  ++i;
												 }
					 b[0]=i-1;
				    }
 if(n%2)for(i=a[0];i>0;--i)g<<a[i];
 else for(i=b[0];i>0;--i)g<<b[i];
 f.close();
 g.close();
 return 0;
}