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