How can I remove the last comma from a loop in C++ in a simple way?

Question

This program is for printing prime numbers till the input given and separating every prime number with a comma.

void main(){

    int N, counter=0, isPrime;

    int k, j;

    cout << "Enter maximum range: ";

    cin >> N;

    for (j=2; j<=N; j++){

        isPrime = 0;
        k = 2;

        while (k<j){

            if (j%k==0){

                isPrime++;
            }
            k++;
        }
        if (isPrime==0){

            if (k==N){
                cout << j;
            }
            else{
                cout << j << ",";
            }
            counter++;
        }
    }
    cout << endl;
    system("pause");
}

It is only removing the last comma for prime number inputs, not for any other input. How can I fix this?

Input: 23
Output: 2,3,5,7,11,13,17,19,23
Input: 8
Output: 2,3,5,7,
Input: 9
Output: 2,3,5,7,

Solution 1

Don't remove the last comma. Instead insert commas before each entry except the first.

Solution 2

Just decide from a pre condition:

bool first = true;
for(j=2;j<=N;j++){
   // ...
   if(k==N) {
   if(!first) {
       cout << ',';
   }
   else {
       first = false;
   }
   cout<<j;
}