#include<iostream>
#include<cmath>
using namespace std;

int main()
{
    double n,p;cin>>n;
    p=pow(((1+sqrt(5))/2),n)-pow((1-sqrt(5))/2,n);
    printf("%.2lf\n",p/sqrt(5));


    return 0;
 } 

#include<iostream>

using namespace std;

const int N = 100010;
int p[N];

int find(int x)  // ·µ»ØxµÄ×æ×Ú½Úµã+·¾¶Ñ¹Ëõ 
{
    if(p[x] != x)  p[x] = find(p[x]);
     return p[x];
}

int main()
{
    int n,m,l; scanf("%d %d %d",&n,&m,&l);

    for(int i=1;i<=n;i++)
    p[i]=i;

    while(m--)
    {
        int a,b; scanf("%d %d",&a,&b);
        p[find(a)] = find(b);

        }   

    while(l--)
    {
        int x,y; scanf("%d %d",&x,&y);
        if(find(x) == find(y))
        puts("Yes");
        else  puts("No");
    }

    return 0;
 } 

#include<iostream>

using namespace std;

const int N = 100010;
int p[N];

int find(int x)
{
    if(p[x] != x)
    p[x] = find(p[x]);
    return p[x];

}

int main()
{
    int n,m,l=1; 
    while(~scanf("%d %d",&n,&m))
    {
        if(n==0&&m==0)  break;

        for(int i = 1;i <= n;i++)
         p[i]=i;  


       while(m--)
     {
       int a,b; scanf("%d %d",&a,&b);
       if(find(a) != find(b))
       p[find(a)] = find(b); 
      }
     int k=0;
       for(int i=1;i<=n;i++)
      {
        if(p[i] == i)
        k++;
       }
      printf("Case %d: %d\n",l,k);
      l++; 
    }



    return 0;
 }