n, m = map(int, input().split())
S = input()
T = input()
dp = [[0] * (m + 1) for _ in range(n + 1)]
for i in range(1, n + 1):
    dp[i][0] = i
for j in range(1, m + 1):
    dp[0][j] = i

for i in range(n):
    for j in range(m):
        dp[i + 1][j + 1] = min(dp[i][j], dp[i][j + 1], dp[i + 1][j]) + 1
        if S[i] == T[j]:
            dp[i + 1][j + 1] = min(dp[i + 1][j + 1], dp[i][j])
print(dp[-1][-1])