#include<fstream.h>
long long v[50];
int a[1000],b[1000],aux,t=0,i,j,n;
int main()
{
ifstream f("nunta.in");
ofstream g("nunta.out");

 f>>n;

v[1]=1;
v[2]=2;

if(n<=45)

 {for(i=3;i<=n;i++)

  v[i]=v[i-1]+v[i-2];

g<<v[n];
 }
else


 {
   for(i=3;i<=45;i++)

    v[i]=v[i-1]+v[i-2];

   aux=v[44]; i=0;

   while(!aux)

    { a[++i]=aux%10; aux/=10;}    a[0]=i;

    aux=v[45]; i=0;

   while(!aux)

    { b[++i]=aux%10; aux/=10;}    b[0]=i;

   for(j=46;j<=n;j++)
   {

    for(i=1;i<=a[0]||i<=b[0]||t;i++,t/=10)

    { aux=b[i];

     b[i]= (t+=a[i]+b[i])%10;

      a[i]=aux; }

      b[0]=i-1;  t=0;
    }
for(i=b[0];i>=1;i--)
 g<<b[i];
}



f.close();
g.close();
return 0;
}