#include<fstream>

#define Nmax 250

using namespace std;

int n, v[2][Nmax], t;

bool ok;

int main()
{
    ifstream f("nunta.in");
    ofstream h("nunta.out");
    f >> n;
    f.close();

    if (n == 1)
        h << "1\n";
    else
        if (n == 2)
            h << "2\n";
        else
        {
            v[0][0] = 1;
            v[0][1] = 1;
            v[1][0] = 1;
            v[1][1] = 2;
            n = n - 2;
            ok = 0;
            for (int i = 1; i <= n; ++i)
            {
                t = 0;
                int j;
                for (j = 1; j <= v[ok][0] || j <= v[!ok][0] || t; ++j)
                {
                    v[ok][j] += v[!ok][j] + t;
                    t = v[ok][j] / 10;
                    v[ok][j] %= 10;
                }
                v[ok][0] = j - 1;
                ok = !ok;
            }
            ok = !ok;
            for (int i = v[ok][0]; i >= 1; --i)
                h << v[ok][i];
            h << '\n';
        }

    h.close();
    return 0;
}