#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

int main(){
    int n, m;
    while(cin >> n >> m){
        string S, T;
        cin >> S >> T;
        vector<vi> dp(n+1, vi(m+1, 10000));
        dp[0][0] = 0;
        rep(i, n + 1)rep(j, m + 1){
            int val = dp[i][j];
            if(i < n&&j < m&&S[i] == T[j])
                smin(dp[i + 1][j + 1], val);
            if(i < n)smin(dp[i + 1][j], val + 1);
            if(j < m)smin(dp[i][j + 1], val + 1);
            if(i < n&&j < m)smin(dp[i + 1][j + 1], val + 1);
        }
        cout << dp[n][m] << endl;
    }
}