[Closed] Cannot convert types?

I have been working on random generation of objects and I came across an error, like I always do, and I can't figure this one out. I have been trying to set certain parts of the heightmap, and this was just a test to see if it would work, but the types aren't converting like they should! it says that in the for loop it can't convert the Heightmap[x, y] to Heightmap[buildingPlacementX, buildingPlacementY] when it should be able to...

 public void GenerateBuilding(Terrain buildingTerrain, GameObject building) {
         
         TD = buildingTerrain.terrainData;
         Heightmap = new float[TD.heightmapWidth, TD.heightmapHeight];
         
         float buildingPlacementX = Random.Range(10f, TD.size.x - 10f);
         float buildingPlacementZ = Random.Range(10f, TD.size.z - 10f);
         int buildingPlacementY = (int)buildingTerrain.SampleHeight(new Vector3(buildingPlacementX, 0, buildingPlacementZ));
         
         Instantiate(building, new Vector3(buildingPlacementX, buildingPlacementY, buildingPlacementZ), Quaternion.identity);
         
         for (float x = 0f; x < (float)TD.heightmapWidth; x++) {
             for (float y = 0f; y < (float)TD.heightmapHeight; y++) {
                 
                 if (Heightmap[x, y] == Heightmap[buildingPlacementX, buildingPlacementZ]) {
                     
                     Heightmap[x, y] = (float)buildingPlacementY;
                     
                 }
             }
         }
         
         TD.SetHeights(0, 0, Heightmap);
     }