#include <bits/stdc++.h>
#define all(x) x.begin(), x.end()
#define pb push_back
#define eb emplace_back
#define rz resize
#define MP make_pair
#define MT make_tuple
#define IT iterator
#define fi first
#define se second
#define For(i, a, b) for (int i = (int)(a); i <= (int)(b); ++i)
#define Rep(i, a, b) for (int i = (int)(a); i >= (int)(b); --i)
#define CLR(a, v) memset(a, v, sizeof(a))
#define CPY(a, b) memcpy(a, b, sizeof(a))
#define debug cerr << "ztxakking\n"
#define y0 ztxaknoi
#define y1 ztxakioi
using namespace std;
using ll = long long;
using ld = long double;
using ull = unsigned long long;
using uint = unsigned int;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pli = pair<ll, int>;
using pil = pair<int, ll>;
using vi = vector<int>;
template<typename T>
using V = vector<T>;
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
const int N = 1e5 + 7;
const ull bas = 233, basInv = 7204522363551799129ull;
int n, ans;
ull pw[N], inv[N];
struct Hash {
  string s;
  ull h[N];
  void init(string t) {
    s = t;
    For(i, 1, n) h[i] = h[i - 1] + s[i] * pw[i - 1];
  }
  ull qry1(int l, int r) {
    return (h[r] - h[l - 1]) * inv[l - 1];
  }
  ull qry2(int l, int r) {
    return qry1(n - r + 1, n - l + 1);
  }
} A1, A2, B1, B2;
string a, b;
int main() {
  ios::sync_with_stdio(0), cin.tie(0);
  cin >> n;
  pw[0] = inv[0] = 1;
  For(i, 1, n) pw[i] = pw[i - 1] * bas, inv[i] = inv[i - 1] * basInv;
  cin >> a >> b, a = '@' + a + '#', b = '@' + b + '$';
  A1.init(a), reverse(all(a)), A2.init(a), reverse(all(a));
  B1.init(b), reverse(all(b)), B2.init(b), reverse(all(b));
  For(i, 1, n) {
    int l1 = 1, r1 = min(i, n - i + 1);
    while (l1 < r1) {
      int mid = l1 + r1 + 1 >> 1;
      if (A1.qry1(i, i + mid - 1) == A2.qry2(i - mid + 1, i)) l1 = mid; else r1 = mid - 1;
    }
    int p = i + l1 - 1, l2 = 0, r2 = min(i - l1, n - p + 1);
    while (l2 < r2) {
      int mid = l2 + r2 + 1 >> 1;
      if (A2.qry2(i - l1 - mid + 1, i - l1) == B1.qry1(p, p + mid - 1)) l2 = mid; else r2 = mid - 1;
    }
    ans = max(ans, (l1 << 1) + (l2 << 1) - 1);
  }
  For(i, 1, n - 1) {
    int l1 = 0, r1 = min(i, n - i);
    while (l1 < r1) {
      int mid = l1 + r1 + 1 >> 1;
      if (A1.qry1(i + 1, i + mid) == A2.qry2(i + 1 - mid, i)) l1 = mid; else r1 = mid - 1;
    }
    int p = i + l1, l2 = 0, r2 = min(i - l1, n - p + 1);
    while (l2 < r2) {
      int mid = l2 + r2 + 1 >> 1;
      if (A2.qry2(i - l1 - mid + 1, i - l1) == B1.qry1(p, p + mid - 1)) l2 = mid; else r2 = mid - 1;
    }
    ans = max(ans, (l1 << 1) + (l2 << 1));
  }
  For(i, 1, n) {
    int l1 = 1, r1 = min(i, n - i + 1);
    while (l1 < r1) {
      int mid = l1 + r1 + 1 >> 1;
      if (B1.qry1(i, i + mid - 1) == B2.qry2(i - mid + 1, i)) l1 = mid; else r1 = mid - 1;
    }
    int p = i - l1 + 1, l2 = 0, r2 = min(p, n - (i + l1) + 1);
    while (l2 < r2) {
      int mid = l2 + r2 + 1 >> 1;
      if (A2.qry2(p - mid + 1, p) == B1.qry1(i + l1, i + l1 + mid - 1)) l2 = mid; else r2 = mid - 1;
    }
    ans = max(ans, (l1 << 1) + (l2 << 1) - 1);
  }
  For(i, 1, n - 1) {
    int l1 = 0, r1 = min(i, n - i);
    while (l1 < r1) {
      int mid = l1 + r1 + 1 >> 1;
      if (B1.qry1(i + 1, i + mid) == B2.qry2(i + 1 - mid, i)) l1 = mid; else r1 = mid - 1;
    }
    int p = i + 1 - l1, l2 = 0, r2 = min(p, n - (i + l1 + 1) + 1);
    while (l2 < r2) {
      int mid = l2 + r2 + 1 >> 1;
      if (A2.qry2(p - mid + 1, p) == B1.qry1(i + l1 + 1, i + l1 + 1 + mid - 1)) l2 = mid; else r2 = mid - 1;
    }
    ans = max(ans, (l1 << 1) + (l2 << 1));
  }
  cout << ans << '\n';
  cerr << (double)(clock()) / CLOCKS_PER_SEC << '\n';
  return 0;
}