suteru=input()
S=input()
T=input()
ls = len(S)
lt = len(T)
dp = [[0]*(ls+1) for _ in range(lt+1)]
for i in range(lt+1):
    dp[i][0] = i
for j in range(ls+1):
    dp[0][j] = j

for i in range(1,lt+1):
    for j in range(1,ls+1):
        if S[j-1] == T[i-1]:
            dp[i][j] = dp[i-1][j-1]
        else:
            dp[i][j] = min(dp[i-1][j],dp[i][j-1],dp[i-1][j-1]) + 1
print(dp[lt][ls])