def Levenshtein_dist(S,T):
    s=len(S)
    t=len(T)
    dp=[[1145141919810931 for i in range(t+1)] for j in range(s+1)]
    dp[0][0]=0

    for i in range(-1,s):
        for j in range(-1,t):
            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[s][t]

  
_,_=map(int,input().split())
S=input()
T=input()
print(Levenshtein_dist(S,T))