#include <fstream>

using namespace std;

ifstream fin ("nunta.in");
ofstream fout ("nunta.out");

struct lol
{
     int nr;
     int sir[1000];
}a,b,c;

int n;

void suma()
{
     c.nr=a.nr;
     if (c.nr<b.nr)
          c.nr=b.nr;
     int t=0;
     for (int i=0;i<c.nr;i++)
     {
          c.sir[i]=a.sir[i]+b.sir[i]+t;
          t=c.sir[i]/10;
          c.sir[i]%=10;
     }
     if (t)
          c.sir[c.nr++]=t;
     a=b;
     b=c;
}

int main ()
{
     fin>>n;
     a.sir[0]=1;
     b.sir[0]=1;
     a.nr=1;
     b.nr=1;
     for (int i=2;i<=n;i++)
          suma();
     for (int i=b.nr-1;i>=0;i--)
          fout<<b.sir[i];
return 0;
}