C#, Unity, creating unique pair of numbers[not working]

I'm trying to create some pairs of unique numbers using pretty simple algorithm. For some unknown reason after compiling Unity goes into an endless "not responding" state. Seems like it's stuck in a do..while loop, but I don't see any reason for that.

 //Creating two lists to store random numbers
    List<int> xList = new List<int>();
    List<int> yList = new List<int>();
    int rx, ry;

    for(int i = 0; i < 10; i++) 
    {
            
        // look for numbers until they are unique(while they are in lists)
        do 
        {
            rx = rand.Next(0, width);
            ry = rand.Next(0, height);
        }
        while(xList.Contains(rx) || yList.Contains(ry));
        
        //add them to lists
        xList.Add(rx);
        yList.Add(ry);
        
        Debug.Log(rx + ", " + ry);
        
        // some actions with these numbers
        gridArray[rx,ry].isBomb = true;
        gridArray[rx,ry].changeSprite(bombSprite);
            
    }