A boy named Mohan was very fond of integer arrays and loved performing various operations on them.
Once he decided to calculate a unique value of the array, which he named as Babua value.
To find that value, he calculates the absolute difference between all consecutive elements in an array 
and adds it to the first element of the array for a permutation.
He does this for all permutations of the array and finds the average value.
He calls this value as Babua Value of array.
Your task is to find this value given an array.

Input

First line of input contains x (2 ≤ x ≤ 100000).
Next line contains x integers a1, a2, ..., ax (1 ≤ ai ≤ 10000000).
All the integers will be distinct.

Output

Output two integers separated by '/'. The first integer being the numerator and second integer being the denominator of a fraction
which is equal to the Babua value. The fraction must be irreducible.

SAMPLE INPUT
3
1 2 4

SAMPLE OUTPUT
19/3

Explanation

Consider 6 possible permutations:

[1, 2, 4]: total sum for a permutation: 1 + |2 – 1| + |4 – 2| = 4;
[1, 4, 2]:  1 + |4 – 1| + |2 – 4| = 6;
[2, 1, 4]:  2 + |1 – 2| + |4 – 1| = 6;
[2, 4, 1]:  2 + |4 – 2| + |1 – 4| = 7;
[4, 1, 2]:  4 + |1 – 4| + |2 – 1| = 8;
[4, 2, 1]:  4 + |2 – 4| + |1 – 2| = 7.
The average travel distance is  = 19/3.
def gcd(a,b):
	if (a%b==0):
		return b
	return gcd(b,a%b)
	
z=input()
a=map(int,raw_input().split())
a=sorted(a)
ans=0
for x in a:
	ans+=x
	
	
#for x in a:
#	for y in a:
#		ans+=abs(x-y)

start=0
aa=0
count=0
for x in a:
	aa+=2*(count*x-start)
	start+=x
	count+=1
	
ans+=aa
num=ans
den=z
g=gcd(num,den)
num,den=num/g,den/g
print str(num)+"/"+str(den)