#include <bits/stdc++.h>
using namespace std;
int dirx[] = {1, -1, 0, 0, 1, 1, -1, -1}, diry[] = {0, 0, 1, -1, 1, -1, 1, -1};
bool Set(int n, int pos) { return bool(n & (1 << pos)); }
int32_t main() {
  ios_base::sync_with_stdio(false);
  int n, m;
  cin >> n >> m;
  string a, b;
  cin >> a >> b;
  int dp[n + 1][m + 1], ans = -1;
  memset(dp, 0, sizeof(dp));
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      dp[i][j] = max(0, 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);
      ans = max(ans, dp[i][j]);
    }
  }
  cout << ans;
  return 0;
}
