#include <stdio.h>
#include <string.h>

short int a[300],b[300],c[300];
int n,i;

void adunam()
{
     int i,x,tin=0;
     for (i=1;i<=b[0]+1;i++){
        x=a[i]+b[i]+tin;
        tin=x/10;
        c[i]=x%10;
        if (c[i]>0) c[0]=i;
        }
}

int main ()
{
    freopen ("nunta.in","r",stdin);
    freopen ("nunta.out","w",stdout);
    
    scanf ("%d",&n);
    a[0]=1, a[1]=1, b[0]=1, b[1]=2;
    
    if (n==1) printf ("1");
    else if (n==2) printf ("2");
    else 
         for (i=3;i<=n;i++){
             adunam();
             memcpy(a,b,sizeof(a));
             memcpy(b,c,sizeof(b));
             }
        
    for (i=b[0];i>0;i--) printf ("%d",b[i]);
    
    return 0;
}