class Solution {
public:
    int removeDuplicates(vector<int>& A) {
        int index=0;
        
        for(int i=0;i<A.size();i++){
            int j=i;
            while(j<A.size()&&A[j]==A[i]){
                j++;
            }
            if(j-1-i==0){//one elements
                A[index++]=A[j-1];
            }
            else{
                A[index++]=A[j-1];
                A[index++]=A[j-1];
            }
            i=j-1;
        }
        return index;
    }
};