def levenstein_distance(a, b):
        la, lb = len(a), len(b)
        if min(la, lb) == 0: return max(la, lb)

        A = [[0] * (lb + 1) for i in xrange(la + 1)]
        for i in xrange(la + 1): A[i][0] = i
        for i in xrange(lb + 1): A[0][i] = i

        for i in xrange(1, la + 1):
                for j in xrange(1, lb + 1):
                        if a[i - 1] == b[j - 1]:
                                A[i][j] = A[i - 1][j - 1]
                        else:
                                A[i][j] = min(A[i - 1][j], A[i][j - 1], A[i - 1][j - 1]) + 1
        return A[la][lb]

n, m = map(int, raw_input().split())
s = raw_input()
t = raw_input()
print levenstein_distance(s, t)