Minimum Fuel Stops to Destination

You are driving along a straight highway of total length `roadLength` miles. Your car starts with `startFuel` units of fuel. Along the road there are `n` fuel stations, each described by `[position, fuelAmount]`, where `position` is the distance from the start and `fuelAmount` is how much fuel you can pick up there.

Your car consumes exactly 1 unit of fuel per mile. You want to reach the destination (at mile `roadLength`) stopping at the **fewest** number of stations possible.

Return the minimum number of fuel stops needed to reach the destination, or `-1` if it is impossible.

**Example 1:**
```
Input: roadLength = 100, startFuel = 10, stations = [[10,60],[20,30],[30,40],[60,40]]
Output: 2
Explanation: Stop at station 0 (pick up 60), then stop at station 3 (pick up 40). Total stops = 2.
```

**Example 2:**
```
Input: roadLength = 50, startFuel = 5, stations = [[25,10]]
Output: -1
Explanation: Cannot reach mile 25 with only 5 units of fuel.
```