public class Solution {
    public int RemoveDuplicates(int[] nums) {
        var k = nums.Length;
        var putIndex = 0;
        for(var i = 0; i < nums.Length; i++)
        {
            while(i < nums.Length - 1 && nums[i+1] == nums[i])
            {
                i++;
                k--;
            }
            nums[putIndex++] = nums[i];
        }
        return k;
    }
}