#include <fstream>
#include <cstring>

using namespace std;

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 n;
int x[250], y[250], tmp[250];

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

    f >> n;

    if(n == 1)
    {
        g << 1;
        return 0;
    }
    if(n == 2)
    {
        g << 2;
        return 0;
    }


    x[0] = 1;
    y[0] = 1;
    x[1] = 1;
    y[1] = 2;

    for(int i = 2; i <= n; i++)
    {
        memcpy(tmp, y, sizeof(int)*250);
        add(y, x);
        memcpy(x, tmp, sizeof(int)*250);
    }


    for(int i = x[0]; i > 0; i--)
        g << x[i];


    return 0;
}