import sys

sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def U(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N,M = MI()
S = ' '+U()
T = ' '+U()

dp = [[10000]*(M+1) for _ in range(N+1)]
dp[0][0] = 0
for i in range(1,N+1):
    dp[i][0] = i
for j in range(1,M+1):
    dp[0][j] = j

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

print(dp[-1][-1])