class Solution {
public:
   int minRefuelStops(int target, int startFuel, vector<vector<int>>& stations) {
      int len = stations.size();
      vector<long> dp(len + 1, 0);
      dp[0] = startFuel;
      for (int i = 0; i < len; ++i)
      {
         for (int j = i + 1; j > 0; --j)
         {
            if (dp[j - 1] >= stations[i][0])
               dp[j] = max(dp[j], dp[j - 1] + static_cast<long>(stations[i][1]));
         }
      }
      for (int i = 0; i <= len; ++i)
         if (dp[i] >= target)return i;
      return -1;
   }
};