// C# Program to compute sum

// of prime number in a given range

using System;

class Prime

{

// Method to compute the prime

// number Time Complexity is O(sqrt(N))

static bool checkPrime(int numberToCheck)

{

    if(numberToCheck == 1)

    {

        return false;

    }

    for (int i = 2;

             i * i <= numberToCheck; i++)

    {

        if (numberToCheck % i == 0)

        {

            return false;

        }

    }

    return true;

}

// Method to iterate the loop from l to r

// If prime number detects, sum the value

static int primeSum(int l, int r)

{

    int sum = 0;

    for (int i = r; i >= l; i--)

    {

        // Check for prime

        bool isPrime = checkPrime(i);

        if (isPrime)

        {

            // Sum the prime number

            sum = sum + i;

        }

    }

    return sum;

}

// Time Complexity is O(r x sqrt(N))

// Driver code

public static void Main()

{

    int l = 4, r = 13;

    // Call the method with l and r

    Console.Write(primeSum(l, r));

}

}

// This code is contributed

// by ChitraNayal