n, m = map(int, input().split())
s = input()
t = input()
dp = [[float("inf")] * (m + 1) for i in range(n + 1)]
dp[0][0] = 0
for i in range(n + 1):
    for j in range(m + 1):
        if i == j == -1:
            continue
        if i > 0 and j > 0:
            if s[i - 1] == t[j - 1]:
                dp[i][j] = min(dp[i][j], dp[i - 1][j - 1])
            else:
                dp[i][j] = min(dp[i][j], dp[i - 1][j - 1] + 1)
        if i > 0:
            dp[i][j] = min(dp[i][j], dp[i - 1][j] + 1)
        if j > 0:
            dp[i][j] = min(dp[i][j], dp[i][j - 1] + 1)
print(dp[n][m])