#include <bits/stdc++.h>
using namespace std;
const int N = 5001;
int dp[N][N];
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n, m;
  cin >> n >> m;
  string a, b;
  cin >> a >> b;
  for (int i = 0; i <= n; i++) fill(dp[i], dp[i] + m + 1, 0);
  int ans = 0;
  for (int i = 1; i <= n; i++)
    for (int j = 1; j <= m; j++) {
      dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]) - 1;
      if (a[i - 1] == b[j - 1]) dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 2);
      dp[i][j] = max(dp[i][j], 0);
      ans = max(ans, dp[i][j]);
    }
  cout << ans << '\n';
  return 0;
}
