Non repeating elements from array

#include <iostream>
#include <stdlib.h>
#include <time.h>

int main()
{
    srand(time(NULL)); //initialize the random seed

    while (true) {
        const char arrayNum[4] = { '1', '3', '7', '9' };
        int RandIndex = rand() % 4; //generates a random number between 0 and 3
        cout << arrayNum[RandIndex];
    }
}

When generating this numbers some of them are repeating and i don't want this.Is a way for this?