class Solution {
public:
    int numRabbits(vector<int>& answers) {
        unordered_map<int, int> cnt;
        for (int i: answers) {
            ++cnt[i];
        }

        int res = 0;
        for (auto [k, v] : cnt) {
            res += (v + k) / (k + 1) * (k + 1);
        }
        return res;
    }
};