Generate a Python function that takes in a list of numbers and returns the greatest common divisor (GCD) of the list elements.
[25, 15, 20]
def find_GCD(input_list): 
 gcd = input_list[0] 
 for num in input_list[1:]: 
 gcd = find_GCD(gcd, num) 
 return gcd

def find_GCD(a, b):
 while(b != 0): 
 a, b = b, a%b 
 return a