#include<fstream>
#include<cstring>
#define maxv 500

using namespace std;

ifstream f("nunta.in");
ofstream g("nunta.out");

int n,a[maxv],b[maxv],c[maxv],i;

void add(int A[], int B[])
{
      int 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;
}

int main()
{
    a[0]=1;
    a[1]=0;
    b[0]=1;
    b[1]=1;

    f>>n;

    for(i=1;i<=n;++i)
    {
        memset(c,0,sizeof(c));
        add(c,a);
        add(c,b);
        memset(a,0,sizeof(a));
        add(a,b);
        memset(b,0,sizeof(b));
        add(b,c);
    }

    for(i=c[0];i;--i)
        g<<c[i];
    g<<"\n";

    f.close();
    g.close();

    return 0;
}