public static long aVeryBigSum(List<long> ar)
    {   
        // long sum =0;
        // foreach(int i in ar)
        // {
        //     sum+=i;
        // }
        // return sum;
        long sum=0;
        for (int i=0; i<ar.Count;i++)
        {
            sum+=ar[i];
        }
        return sum;
    }

public static long aVeryBigSum(List<Long> numbers) {
    long sum = 0;
    
    // Iterate through all items of given
    // list to calculate sum
    for(long number : numbers) {
        sum = sum + number;
    }
    
    return sum;
}

public static long aVeryBigSum(List<Long> numbers) {
    //Calculate sum using reduce
    return numbers.stream()
        .reduce(Long::sum)
        .get();
}

public static long aVeryBigSum(List<Long> numbers) {
    // Base case: if the current list is emtpty
    // return 0
    if(numbers.isEmpty()) return 0;
    
    // Get the current value from the list
    long current = numbers.get(numbers.size() - 1);
    
    // Remove the current value
    numbers.remove(numbers.size() - 1);
    
    // Recursive call: calculate the sum of
    // the current value and the rest numbers
    return current + aVeryBigSum(numbers);
}

long aVeryBigSum(int ar_count, long* ar) {

    long retVal;

    int count=0;
    long temp =0;
    
    for (int i=0;i<ar_count;i++)
    {
        temp = ar[i]%1000000000;
        retVal +=temp;
        count++;
    }
    
return (retVal+(count*(ar[0]-(ar[0]%1000000000))));
}