N,M = map(int,input().split())
S = input()
T = input()
DP = [[10**5]*(M+1) for _ in range(N+1)]
DP[0][0]=0
for i in range(N+1):
    for j in range(M+1):
        if i<N and j<M :
            if S[i]==T[j]:
                DP[i+1][j+1]=min(DP[i+1][j+1],DP[i][j])
            else:
                DP[i+1][j+1]=min(DP[i+1][j+1],DP[i][j]+1)
        if i<N:
            DP[i+1][j]=min(DP[i+1][j],DP[i][j]+1)
        if j<M:
            DP[i][j+1]=min(DP[i][j+1],DP[i][j]+1)

print(DP[N][M])