n, m = map(int, input().split())
s = input()
t = input()
dp = [[1001]*(m+1) for _ in range(n+1)]
dp[n][m] = 0
for i in range(n)[::-1]:
    for j in range(m)[::-1]:
        dp[i][j] = min(
                int(s[i]!=t[j]) + dp[i+1][j+1],
                1 + dp[i+1][j],
                1 + dp[i][j+1])
print(dp[0][0])