#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int n, m;
string s, t;
int dp[1001][1001];

int main() {
	cin >> n >> m >> s >> t;
	
	fill(dp[0], dp[1001], INF);
	
	dp[0][0] = 0;
	
	REP(i, n + 1) {
		REP(j, m + 1) {
			if (i != n && j != m) {
				if (s[i] == t[j]) chmin(dp[i + 1][j + 1], dp[i][j]);
				else chmin(dp[i + 1][j + 1], dp[i][j] + 1);
			}
			
			if (j < m) chmin(dp[i][j + 1], dp[i][j] + 1);
			if (i < n)chmin(dp[i + 1][j], dp[i][j] + 1);
		}
	}
	
	cout << dp[n][m] << endl;
	
	return 0;
}