#include <fstream.h>

int n,a[2500],b[2500],c[2500],nr;
void citire()
{
   ifstream fin("nunta.in");
   fin>>n;
   fin.close();
}

void suma()
{
   a[2000]=1;
   b[2000]=1;
   nr=1;
   int t=0;
   for (int i=0;i<n;i++)
   {
   t=0;
   for (int l=0;l<=2000;l++)
   {
       int aux=a[l];
       a[l]=b[l];
       b[l]=aux;
   }
     for (int j=2000;j>2000-nr;j--)
     {
	a[j]+=b[j]+t;
	t=a[j]/10;
	a[j]=a[j]%10;
     }
   if (t==1)
      a[2000-(nr++)]=1;
   }
}

void afisare()
{
   ofstream fout("nunta.out");
       if (n==1)
       fout<<"1";
       else
    if (n==2)
       fout<<"2";
       else
       {
   for (int i=2000-nr+1;i<=2000;i++)
      fout<<b[i]; }
   fout<<"\n";
   fout.close();
}

int main()
{
   citire();
   suma();
   afisare();
   return 0;
}