# Exp2 generates n with probability 1/2^(n+1).                               
    @staticmethod                                                                
    def _rand_exp():                                                                                                                                                                   
        rand_bin = bin(int(random.random() * 2**32-1))[2:]                       
        rand_bin = '0'*(32 - len(rand_bin)) + rand_bin                           
        count = 0                                                                
        for i in rand_bin:                                                       
            if i == '0':                                                         
                count +=1                                                        
            else:                                                                
                break                                                            
        return count