def Levenshtein_dist(S,T):
  m=len(S)
  n=len(T)
  inf=float("inf")
  dp=[[inf for i in range(n+1)] for j in range(m+1)]
  dp[0][0]=0

  for i in range(-1,m):
    for j in range(-1,n):
      if i==-1 and j==-1:
        continue
      elif i>=0 and j>=0:
        if S[i]==T[j]:
          dp[i+1][j+1]=min(dp[i][j],dp[i][j+1]+1, dp[i+1][j]+1)
        else:
          dp[i+1][j+1]=min(dp[i][j]+1,dp[i][j+1]+1, dp[i+1][j]+1)
      elif i>=0:
        dp[i+1][j+1] = dp[i][j+1]+1
      elif j>=0:
        dp[i+1][j+1] = dp[i+1][j]+1
  return dp[m][n]
  
s,t=map(int,input().split())
S=input()
T=input()
print(Levenshtein_dist(S,T))