n, m = map(int, input().split())
s = input()
t = input()
memo = {}
def dfs(i, j):
    if i == n and j == m:
        return 0
    if (i,j) in memo:
        return memo[i,j]
    res = 1001
    if i < n and j < m:
        res = min(res, int(s[i]!=t[j]) + dfs(i+1, j+1))
    if i < n:
        res = min(res, 1 + dfs(i+1, j))
    if j < m:
        res = min(res, 1 + dfs(i, j+1))
    memo[i,j] = res
    return res
print(dfs(0, 0))