#include <stdio.h>
int t,i,j,k,n;
int a[301],b[301],c[301];
int main()
{
	freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);
    
    scanf("%d",&n);
    a[300]=1;
    b[300]=2;
    if (n==1) c[300]=1;
    if (n==2) c[300]=2;
    for (k=3; k<=n; k++)
    {
        t=0;
        for (i=300; i>=1; i--)
        {
           c[i]=0; 
           c[i]=a[i]+b[i]+t;
           t=c[i]/10;
           c[i]=c[i]%10;
        }    
        for (i=1; i<=300; i++)
        {
            a[i]=b[i];
            b[i]=c[i];    
        }
    }   
    for (i=1; i<=300; i++)
		if (c[i+1]!=0)
		{
		   j=i+1;
		   break;
		}
	for (i=j; i<=300; i++)
		printf("%d",c[i]);


	return 0;
}