combineSharedBlocks := make(map[int][]byte)
		combineFilledBlocks := make(map[int][]byte)
	nextFile:
		for key, file := range files[partIdx] {
			fmt.Println("Reading base version", file[0], "part", part)
			var combined []byte
			var missingAll int
			var lastValidAll int

			attempt := 0
			for block := 0; ; block++ {
				combineFilled := combineFilledBlocks[block]
				combineShared := combineSharedBlocks[block]