Codeground is hosting the World's largest coding competition. There are N participants in the contest sitting in a single row.

The energy of iβth participant from left is A[i]. To raise the popularity of the contest, some rules are added.

A participant numbered i will challenge other participant numbered j if and only if j is ahead of him (j>i) and the distance between i and j (j-i) is prime.

The contest popularity value of participant i challenging participant j is A[j]-A[i]. The total contest popularity value of the competition is sum of popularity value of all such challenges.

Given the energy of all participants, you have to find the total popularity value.

**INPUT**

The first line contains N, the number of participants. The next line contains N space separated integers representing the energy of all the participants.

**OUTPUT**

Print a single line containing the total popularity value.

**CONSTRAINTS
**

1<=N<=1000

1 <=A[i]<= 1000000000

**EXPLANATION OF SAMPLE**

1 Sample input has N as 7 and participants energy as 24 6 8 10 12 14. 2. The contest popularity based on rules described is as below:

j-i val diff

5-0=5 12-2=10

3-0=3 8-2 = 6

2-0=2 6-2 = 4

6-1=5 14-4 = 10

4-1=3 10-4 = 6

3-1=2 8-4 = 4

5-2=3 12-6 = 6

4-2=2 10-6 = 4

6-3=3 14-8= 6

5-3=2 12-8 = 4

6-4=2 14-10=4

Total 64

**Sample Input**

7 2 4 6 8 10 12 14

**Sample Output**

64

**Code(python 3)**

```
def solution(n,A):
sum=0
for i in range(n):
for j in range(n):
if(j>i):
num=j-i
if(prime(num)):
sum=sum+(A[j]-A[i])
return sum
def prime(n):
if n==1:
return False
for i in range(2,int(n/2)+1):
if n%i==0:
return False
return True
n=int(input())
A=list(map(int,input().split()))[:n]
print(solution(n,A))
```

More at : https://onlylang.blogspot.com/

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