#include <iostream.h>
#include <string.h>
#include <fstream.h>
fstream f("nunta.in",ios::in);
fstream g("nunta.out",ios::out);
int a[1001],b[1001],s[1001];
int i,j,k,t,x,n,d;

int main ()
{
  f>>n;
  a[1]=1;
  b[1]=1;
  k=1;
  for (i=2;i<=n;++i)
	{
	  t=0;
	  for (j=1;j<=k;j++)
		{
		  x=a[j]+b[j]+t;
		  s[j]=x%10;
		  t=x/10;
		 }
	  if (t>0) s[++k]=t;
	  for (j=1;j<=k;++j)
		{
		  a[j]=b[j];
		  b[j]=s[j];
		 }
	 }
  if (n==1) g<<"1";
	else for (i=k;i>0;--i) g<<s[i];
  return 0;
}