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