#include <cstdio>
using namespace std;
char a[205], b[205], c[205];
short na, nb, nc;
int n;
/// c = a + b
inline void Aduna()
{
    short i, t, x;
    t = 0;
    nc = nb;
    for (i = 1; i <= nb; ++i)
    {
        x = (a[i]-'0') + (b[i]-'0') + 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;
    freopen("nunta.out", "w", stdout);
    freopen("nunta.in", "r", stdin);
    scanf("%d", &n);
    if (n == 1)
    {
        printf("1\n");
        return 0;
    }
    if (n == 2)
    {
        printf("2\n");
        return 0;
    }
    for (i = 0; i <= 204; ++i)
        a[i] = b[i] = c[i] = '0';
    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)
        printf("%c", c[i]);
    printf("\n");
    return 0;
}