```
def lcs(self, s1, s2):
m, n = len(s1), len(s2)
dp = [[0] * (n + 1) for _ in range(m + 1)]
for i in range(m):
for j in range(n):
if s1[i] == s2[j]:
dp[i + 1][j + 1] = dp[i][j] + 1
else:
dp[i + 1][j + 1] = max(dp[i][j + 1], dp[i + 1][j])
return dp[m][n]
def minDistance(self, word1, word2):
"""
:type word1: str
:type word2: str
:rtype: int
"""
return len(word1) + len(word2) - 2 * self.lcs(word1, word2)
```