#include <cstdio>

int aux, t, i, T, n, a[2][302];
void add(int a[], int b[]){
    T = 0;
    if(b[0] > a[0])
        a[0] = b[0];
    for(int i = 1; i <= a[0] ; ++i){
        a[i] += b[i] + T;
        T = a[i] / 10;
        a[i] %= 10;
    }
    if(T > 0)
        a[++a[0]] = T;
}
int main()
{
    freopen("nunta.in", "r", stdin);
    freopen("nunta.out", "w", stdout);
    scanf("%d", &n);
    a[0][0] = 1; a[1][0] = 1;
    a[0][1] = 1; a[1][1] = 1;
    for(t = 2; t <= n ; ++t)
        add(a[t & 1], a[1 - (t & 1)]);
    for(t = a[n & 1][0]; t >= 1 ; --t)
        fputc(a[n & 1][t] + '0', stdout);
    return 0;
}