#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;

const int INF = 1<<29; // enough large value

// input
int n, m;
string S, T;

// DP table
int dp[1010][1010];

int main() {
    cin >> n >> m >> S >> T;

    // initialize
    for (int i = 0; i < 1010; ++i) for (int j = 0; j < 1010; ++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; // dp[0][0] has been already considered
            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;
}