def fusc(n):
    assert type(n) == int and n >= 0
    if n == 0:
        return 0
    elif n == 1: 
        return 1 
    elif n % 2 == 0:
        return fusc(int(n/2))
    else:
        return fusc(int((n-1)/2)) + fusc(int((n-1)/2)+1)
    
    
    
print (fusc(25))