#include <bits/stdc++.h>
using namespace std;
int n, m;
string a, b;
int dp[5005][5005];
void solve() {
  cin >> n >> m;
  cin >> a >> b;
  int ans = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (a[i - 1] == b[j - 1])
        dp[i][j] = dp[i - 1][j - 1] + 2;
      else
        dp[i][j] = max(0, max(dp[i - 1][j], dp[i][j - 1]) - 1);
      ans = max(ans, dp[i][j]);
    }
  }
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  ;
  solve();
  return 0;
}
