#include <bits/stdc++.h>
using namespace std;
char a[5005], b[5005];
int n, m, dp[5005][5005], ma = 0;
int main() {
  cin >> n >> m;
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = 1; i <= m; i++) cin >> b[i];
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      dp[i][j] = max(dp[i][j], max(dp[i - 1][j], dp[i][j - 1]) - 1);
      if (a[i] == b[j]) dp[i][j] = max(dp[i][j], dp[i - 1][j - 1] + 2);
      ma = max(ma, dp[i][j]);
    }
  }
  cout << ma;
  return 0;
}
