Why I am getting wrong answer?

well,i was trying this question:https://www.hackerrank.com/contests/may13/challenges/equal and i am getting wrong answer for two test cases can someone tell me where this program is going wrong along with valid solution to it:

#include<stdio.h>


#include<algorithm>
using namespace std;
int main()
{
int t,l1=0,i,n;
long k=0,s1=0,s=0;
int arr[10001];
int arr1[200];
scanf("%d",&t);
while(t--)
{
    scanf("%d",&n);
    for(i=0;i<n;i++)
    scanf("%d",&arr[i]);
    sort(arr,arr+n);
    s1=0;
    for(i=0;i<n-1;i++)
    {

        if(arr[i]!=arr[i+1])
        {
            s=arr[i+1]-arr[i];
            s1+=s;
            if(i!=n-2)
        arr[i+2]+=s1;
            if(s>=5)
            {
                k+=s/5;
                s=s%5;
            }
            if(s>=0)
            {
                k+=s/2;
                s=s%2;
            }

            k+=s;
        }
    }
    printf("%ld\n",k);
//      arr1[l1++]=k;
    k=0;
}
/*  for(i=0;i<l1;i++)
printf("%d\n",arr1[i]);*/
return 0;
}

thankx in advance...