#include <fstream>

using namespace std;

int N, crt[300], prec[300], copie[300];

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

void copiere(int A[], int B[])
{
    for (int i = 0; i <= B[0]; i++)
        A[i] = B[i];
}

void adunare(int A[], int B[])
{
    int i, t = 0;
    for (i = 1 ; i <= A[0] || i <= B[0] || t ; i++)
    {
        t += A[i] + B[i];
        A[i] = t % 10;
        t /= 10;
    }
    A[0] = i - 1;
}

void afisare(int A[])
{
    for (int i = A[0]; i >= 1; i--)
        g << A[i];
}

int main()
{
    f >> N;
    if(N == 1)
        g << '1';
    else
    {
        prec[0] = prec[1] = crt[0] = crt[1] = 1;
        for (int i = 2; i <= N; i++)
        {
            copiere(copie, crt);
            adunare(crt, prec);
            copiere(prec, copie);
        }
        afisare(crt);
    }
    f.close();
    g.close();
    return 0;
}