class VersionManager:
    def __init__(self, version=None):
        if not version:
            version = "0.0.1"

        parts = version.split(".")[:3]

        if not all(p.isdecimal() for p in parts):
            raise ValueError("Error occured while parsing version!")

        nums = [int(p) for p in parts]

        while len(nums) < 3:
            nums.append(0)

        self.major_v, self.minor_v, self.patch_v = nums
        self.history = []

    def _save(self):
        self.history.append((self.major_v, self.minor_v, self.patch_v))

    def major(self):
        self._save()
        self.major_v += 1
        self.minor_v = 0
        self.patch_v = 0
        return self

    def minor(self):
        self._save()
        self.minor_v += 1
        self.patch_v = 0
        return self

    def patch(self):
        self._save()
        self.patch_v += 1
        return self

    def rollback(self):
        if not self.history:
            raise Exception("Cannot rollback!")
        self.major_v, self.minor_v, self.patch_v = self.history.pop()
        return self

    def release(self):
        return f"{self.major_v}.{self.minor_v}.{self.patch_v}"