#include <fstream>
using namespace std;
ifstream in("kfib.in");
ofstream out("kfib.out");
void fibonacci(int k)
{
    int a=1,b=1,c,i;
    for(i=1;i<=k-2;i++)
    {
        c=a+b;
        a=b;
        b=c;
    }
    out<<c;
}

int main()
{
   int k;
   in>>k;
   fibonacci(k);
   in.close();
   out.close();
   return 0;
}