#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,b)  FOR(i,0,b)
#define F first
#define S second
#define PB(a) push_back(a)
#define BE(c) c.begin(),c.end()
using namespace std;
typedef long long LL;
typedef pair<int,long double> pr;
typedef pair<pr,int> ppr;
typedef priority_queue<pr,vector<pr>,greater<pr> > PQ;
typedef vector<pr> Vpr;
typedef vector<LL> VI;
typedef complex<LL> cld;
typedef vector<cld> Vcld;
typedef map<pr,int> MP;
const int SIZE=100010;
const LL INF=1<<28;
string a,b;
int DP[1001][1001];
int solve(int x,int y){
  if(DP[x+1][y+1]) return DP[x+1][y+1];
  if(x!=-1||y!=-1){
    if(x==-1) return DP[x+1][y+1]=solve(x,y-1)+1;
    if(y==-1) return DP[x+1][y+1]=solve(x-1,y)+1;
    if(a[x]==b[y]) return DP[x+1][y+1]=solve(x-1,y-1);
    return DP[x+1][y+1]=min(solve(x,y-1),min(solve(x-1,y-1),solve(x-1,y)))+1;
  }
  return 0;
}
int main(){
  int x,y;
  cin >> x>>y;
  cin >> a >> b;
  cout << solve(a.size(),b.size()) << endl;
  return 0;
}