class Solution {
 public:
  int compress(vector<char>& chars) {
    int ans = 0;

    for (int i = 0; i < chars.size();) {
      const char letter = chars[i];
      int count = 0;
      while (i < chars.size() && chars[i] == letter) {
        ++count;
        ++i;
      }
      chars[ans++] = letter;
      if (count > 1)
        for (const char c : to_string(count))
          chars[ans++] = c;
    }

    return ans;
  }
};