#include "bits/stdc++.h"
using namespace std;

typedef long long ll;

const int INF = 1<<29;

int n, m;
string s, t;
int dp[1100][1100];

int main() {
	cin >> n >> m;
	cin >> s >> t;
	
	for(int i=0; i<1100; i++) for(int j=0; j<1100; j++) dp[i][j] = INF;
	dp[0][0] = 0;

	for (int i = -1; i < (int)s.size(); i++) {
		for (int j = -1; j < (int)t.size(); j++) {
			if(i==-1 && j==-1) continue;
			if (i >= 0 && j >= 0) {
				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>=0) dp[i+1][j+1] = min(dp[i+1][j+1], dp[i][j+1]+1);
			if(j>=0) dp[i+1][j+1] = min(dp[i+1][j+1], dp[i+1][j]+1);
		}
	}

	cout << dp[s.size()][t.size()] << endl;
}