typedef struct sprinker {
        int l;
        int r;
    } sprinkler;

    public:
    int min_sprinklers(int gallery[], int n)
    {
        int freq[n];
        vector<sprinkler> vec;
        for(int i = 0; i < n; i++) freq[i] = 0;
        for(int i = 0 ; i < n; i++) {
            int x = gallery[i];
            if(x == -1) continue;
            int l = max(0, i - x);
            int r = min(n-1, i + x);
            sprinkler s;
            s.l = l;
            s.r = r;
            vec.push_back(s);
            for(int j = l; j <= r; j++) {
                freq[j]++;
            }
        }

        for(int i = 0; i < n; i++) {
            if(freq[i] == 0) return -1;
        }

        stable_sort(vec.begin(), vec.end(), [](sprinkler s1, sprinkler s2) { return s1.r-s1.l < s2.r-s2.l; });

        int sprinklers = vec.size();
        for(int i = 0; i < vec.size(); i++) {
            int l = vec[i].l;
            int r = vec[i].r;
            bool flag = false;
            for(int j = l; j <= r; j++) {
                if(freq[j] == 1) {
                    flag = true;
                    break;
                }
            }

            if(!flag) {
                for(int j = l; j <= r; j++) freq[j]--;
                sprinklers--;
            }
        }

        return sprinklers;
    }
};