class Solution {
public:
    int compress(vector<char>& chars) {

        int i = 0;

        int j = 0;
        int k = 0;

        while(true){

            if (k<chars.size() && chars[j] == chars[k]){
                k++;
                continue;
            }

            int num = k - j;
            chars[i++] = chars[j];
            j = k;

            if (num == 1){
                if (k == chars.size()){
                    break;
                }
                continue;
            }

            string num_str = to_string(num);

            for (auto c : num_str){
                chars[i++] = c;
            }

            if (k == chars.size()){
                break;
            }
        }
        return i;
    }
};