#include<stdio.h>
long long f[101]={1,1};
long long g(int x)
{
    if( x%2 ) return f[x] - f[x/2];
    return f[x] - f[x/2] - f[x/2-1];
}
int main(void)
{
    freopen(".10.in","r",stdin);
    freopen(".10.out","w",stdout);
    int n, i;
    scanf("%lld",&n);
    for( i = 2 ; i <= n ; i++ )
        f[i] = f[i-1] + f[i-2];
    printf("%lld\n",g(n));
    return 0;
}