class Solution {
public:
    double calHourSpent(vector<int>& dist, int speed) {
        int n = dist.size() - 1;
        double hourSpent = 0;

        for(int i = 0; i < n; i++) {
            hourSpent += (dist[i] / speed + (dist[i] % speed != 0));
        }
        
        return hourSpent + (double) dist[n] / speed;
    }

    int minSpeedOnTime(vector<int>& dist, double hour) {
        if(hour <= dist.size() - 1){
            return -1;
        }

        int l = 1;
        int r = 10e7; // two digit decimal after 10e5
        int m;
        double pivot;

        while(l < r) {
            m = l + (r - l) / 2;
            pivot = calHourSpent(dist, m);
            
            if(pivot == hour){
                r = m;
            } else if (pivot > hour){
                l = m + 1;
            } else {
                r = m;
            }
        }

        return r;
    }
};