int main()
{
    long a=0,b=1,c=1;
    int d,n;
    scanf("%d",&n);
    for(d=1;d<=n;d++)
    {
        switch(n)
        {
            case 1:
                printf("0");
                break;
            case 2:
                printf("1");
                break;
            default:
                if(d>=3)
                {
                    c=a+b;
                    a=b;
                    b=c;
                }
                break;
        }
    }
    if(d-1==n)
    {
        printf("%ld",c);
    }
    return 0;
}