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

#define REP(i, n) for(int i=0; i<(n); i++)
#define RREP(i, n) for(int i=(n-1); i>=0; i--)
#define MAX 1111

int N,M;
string S, T;
int dp[MAX][MAX];
signed main()
{
    cin >> N >> M >> S >> T;
    REP(i,M+1) dp[S.size()][i] = M-i;
    RREP(i,N) {
        RREP(j,M) {
            dp[i][j] = min(dp[i+1][j+1] + (S[i] != T[j]), dp[i+1][j] + 1);
            dp[i][j] = min(dp[i][j], dp[i][j+1] + 1);
        }
    }
    cout << dp[0][0] << endl;
    return 0;
}