#include <iostream.h>
#include <fstream.h>
fstream f("nunta.in",ios::in);
fstream g("nunta.out",ios::out);
int  c,n,i,j,w;
int k,t,x;
int q[1001],a[1001],b[1001]; 
int main ()
{
	f>>n;  a[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;
			q[j]=x%10;
			t=x/10;
				 }
		if(t>0){k++;q[k]=t;}
		for(j=1;j<=k;++j){ a[j]=b[j];
				   b[j]=q[j];
				   }
		     }
    if(n==1) g<<"1";
      else  for(i=k;i>0;--i){

		g<<q[i];}
		return 0;
}