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