#include <bits/stdc++.h>
using namespace std;
char a[1005], b[1005], c[1005];
short na, nb, nc, n;
/// c = a + b
inline short Cif(char c)
{
    return c - '0';
}
inline void Aduna()
{
    short i, t, x;
    t = 0;
    nc = nb;
    for (i = 1; i <= nb; ++i)
    {
        x = Cif(a[i]) + Cif(b[i]) + t;
        if (x >= 10) {c[i] = x - 10 + '0'; t = 1;}
        else {c[i] = x + '0'; t = 0;}
    }
    if (t > 0)
        c[++nc] = '1';
}
/// a = b
inline void Copie(char a[], short &na, char b[], short nb)
{
    short i;
    na = nb;
    for (i = 1; i <= na; ++i)
        a[i] = b[i];
}
int main()
{
    short i;
    ofstream fout("nunta.out");
    ifstream fin("nunta.in");
    fin >> n;
    fin.close();

    if (n == 1)
    {
        fout << "1\n";
        fout.close();
        return 0;
    }
    if (n == 2)
    {
        fout << "2\n";
        fout.close();
        return 0;
    }
    memset(a, '0', sizeof(a));
    memset(b, '0', sizeof(b));
    memset(c, '0', sizeof(c));
    a[1] = '1'; na = 1;
    b[1] = '2'; nb = 1;
    for (i = 3; i <= n; ++i)
    {
        Aduna();
        Copie(a, na, b, nb);
        Copie(b, nb, c, nc);
    }
    /// afisare
    for (i = nc; i >= 1; --i)
        fout << c[i];
    fout << "\n";
    fout.close();
    return 0;
}