BES PYTHON SOLUTION WITH 1639MS OF RUNTIME !
\n# Code\npython3 []\nfrom typing import List\n\nclass Solution:\n    def minValidStrings(self, words: List[str], target: str) -> int:\n        n = len(target)\
\n# Code\n```python3 []\nfrom typing import List\n\nclass Solution:\n    def minValidStrings(self, words: List[str], target: str) -> int:\n        n = len(target)\n        dp = [0] * n\n\n        # Function to check if any word starts with the given prefix\n        def hasPrefix(pref):\n            return any(w.startswith(pref) for w in words)\n\n        l, r = 0, 0  # Left and right pointers for window in target\n\n        for i in range(n):\n            # Move left pointer to maintain valid prefix window\n            while not hasPrefix(target[l:r + 1]) and l <= r:\n                l += 1\n            \n            # If no valid prefix found, return -1\n            if l > r:\n                return -1\n\n            # Calculate the length of the valid substring\n            substr_len = r - l + 1\n\n            # Update dp with the minimum number of valid substrings\n            dp[i] = 1 if i < substr_len else dp[i - substr_len] + 1\n\n            # Move the right pointer\n            r += 1\n\n        return dp[-1]  # Return the result for the entire target string\n\n```
['Python3']