using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace pbl_wrapper
{
    class UniqueSetGenerator
    {
        private int[] store_;
        private int size_;
        private Random random_;

        public UniqueSetGenerator(int size, int start)
        {
            size_ = size;
            store_ = new int[size];
            random_ = new Random();
            PopulateArray(start);
        }

        private void PopulateArray(int start)
        {
            for (int i = 0; i < size_; i++)
                store_[i] = start++;
        }

        private int Delete(int pos)
        {
            int val = store_[pos];
            store_[pos] = store_[--size_];
            return val;
        }

        public int GetRandomNumber()
        {
            if (size_ <= 0)
                return -1;

            return Delete(random_.Next(size_));
        }
    }
}