#include<cstdio>

#define Nmax 250

using namespace std;

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

int ok;

int main()
{
    freopen ("nunta.in", "r", stdin);
    freopen ("nunta.out", "w", stdout);
    scanf ("%d", &n);

    if (n <= 3)
        printf ("%d\n", 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)
            printf ("%d", v[ok][i]);
    }

    return 0;
}