class Solution {
public:
   int minRefuelStops(int target, int startFuel, vector<vector<int>>& stations) {
      stations.push_back({target, 0});
      int len = stations.size(), steps = 0, prev = 0;
      long remain = startFuel;
      priority_queue<int> pq;
      for (int i = 0; i < len; ++i)
      {
         int curr = stations[i][0], fuel = stations[i][1];
         remain -= curr - prev;
         while (pq.size() && remain < 0)
         {
            remain += pq.top();
            pq.pop();
            ++steps;
         }

         if (remain < 0)return -1;
         pq.push(fuel);
         prev = curr;
      }
      return steps;
   }
};