Complete the `greatestProduct` method so that it'll find the greatest product of five consecutive digits in the given string of digits.
For example:
The input string always has more than five digits.
Adapted from Project Euler.
def product(list):
    p = 1
    for i in list:
        p *= int(i)
    return p
    
def greatest_product(list):
    res = []
    mul = 1
    while len(list)>= 5:
        res.append(product(list[:5]))
        list = list[1:]
    return(max(res))
        
          

def product(list):
    p = 1
    for i in list:
        p *= int(i)
    return p
    
def greatest_product(list):
    res = []
    mul = 1
    while len(list)>= 5:
        res.append(product(list[:5]))
        list = list[1:]
    return(max(res))
        
          
