# import necessary libraries
import pandas as pd
import math

# define two series
s1 = pd.Series([1, 2, 3])
s2 = pd.Series([4, 5, 6])

# define custom function to calculate Euclidean distance
def euclidean_distance(a, b):
    distance = math.sqrt(sum([(a[i]-b[i])**2 
                              for i in range(len(a))]))
    return distance

# compute Euclidean distance
distance = euclidean_distance(s1, s2)

# print the distance
print(distance)