#include<stdio.h>
int a[1001],i,k,b[1001],c[1001],n,j,t,cc;
using namespace std;
int main(){
	freopen("nunta.in","r",stdin);
	freopen("nunta.out","w",stdout);
	scanf("%d",&n);
	a[0]=1;
	a[1]=2;
	b[0]=1;
	b[1]=1;
	if(n==1)
		printf("1");
	else{
	for(j=1;j<n-1;j++)
	{
		k=0;
	for(i=0;i<=a[0];i++)
		c[i]=a[i];
	t=0;
      for(i=1; i<=a[0] || i<=b[0] || t; i++, t/=10)
              a[i] = (t += a[i] + b[i]) % 10;
      a[0] = i - 1;
	  for(i=0;i<=c[0];i++)
		  b[i]=c[i];
	}
	for(i=a[0];i>=1;i--)
		printf("%d",a[i]);}
	return 0;
}