#ifdef LOCAL111
#else
	#define NDEBUG
#endif
#include <bits/stdc++.h>
const int INF = 1e8;
using namespace std;

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RBP(i,a) for(auto& i : a)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
#else
	#define DEBUG(x) true
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
#define rangej(a,b,c) ((a) <= (c) and (c) < (b))
#define rrangej(b,c) rangej(0,b,c)
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef pair<int,int> P;
typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<LL,LL> LP;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

typedef vector<int> vi;

int n,m;
string s,t;

int memo[1010][1010];

int main()
{
	ios_init();
	while(cin >> n >> m){
		cin >> s >> t;
		REP(i,n) REP(j,m) memo[i][j] = -1;
		if(s[0] == t[0]) memo[0][0] = 0;
		else memo[0][0] = 1;
		function<int(int,int)> dfs = [&](int x, int y) -> int{
			if(memo[x][y] != -1){
				// DEBUG(memo[x][y]);
				return memo[x][y];
			}
			int res = INF;
			if(x != 0 and y != 0) if(s[x] == t[y]){
				res = min(res,dfs(x-1,y-1));
			}else{
				res = min(res,dfs(x-1,y-1)+1);
			}
			if(x != 0) res = min(res,dfs(x-1,y)+1);
			if(y != 0) res = min(res,dfs(x,y-1)+1);
			DEBUG(x); DEBUG(y); DEBUG(res);
			return memo[x][y] = res;
		};
		cout << dfs(n-1,m-1) << endl;
	}
	return 0;
}