n, m = map(int, input().split())
s = "#" + input()
t = "$" + input()

dp = [[1 << 60 for _ in range(m + 1)] for _ in range(n + 1)]
for j in range(m + 1):
  dp[0][j] = j

for i in range(n + 1):
  dp[i][0] = i

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

print(dp[n][m])