#include <bits/stdc++.h>
#define int long long

#define F(i, a, b) for (int i = (a); i <= (b); i++)
#define dF(i, a, b) for (int i = (a); i >= (b); i--)
using namespace std;

typedef unsigned long long ull;
typedef pair<int, int> pii;

const int N = 200005, M = (N << 1), B = 1e7 + 7, inf = 1e9;
int n, ans;
ull pw[N];
mt19937_64 rnd(random_device{}());
struct node {
    string s;
    int h[N], _h[N];
    void init() {
        F(i, 1, n) h[i] = h[i - 1] * B + s[i - 1];
        dF(i, n, 1) _h[i] = _h[i + 1] * B + s[i - 1];
        s = " " + s;
    }
    ull get(int l, int r) {
        if (l < 1 || r > n || l > r) return rnd();
        return h[r] - h[l - 1] * pw[r - l + 1];
    }
    ull _get(int l, int r) {
        if (l < 1 || r > n || l > r) return rnd();
        return _h[l] - _h[r + 1] * pw[r - l + 1];
    }
    bool check(int l, int r) { return get(l, r) == _get(l, r); }
} a, b;
signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
    cin >> n >> a.s >> b.s;
    pw[0] = 1; F(i, 1, n) pw[i] = pw[i - 1] * B;
    a.init(), b.init();
    F(i, 1, n) {
        if (a.s[i] == b.s[i]) {
            int l = 0, r = n, rs = -inf;
            while (l <= r) {
                int mid = (l + r) >> 1;
                if (a.get(i - mid, i) == b._get(i, i + mid)) {
                    l = mid + 1, rs = mid;
                } else r = mid - 1;
            }
            ans = max(ans, rs * 2 + 2);
        }
    }
    F(i, 1, n) {
        int l = 0, r = n, rs = -inf;
        while (l <= r) {
            int mid = (l + r) >> 1;
            if (a.check(i - mid, i + mid)) l = mid + 1, rs = mid; else r = mid - 1;
        }
        int ll = 0, rr = n, ad = 0;
        while (ll <= rr) {
            int mid = (ll + rr) >> 1;
            if (a.get(i - rs - 1 - mid, i - rs - 1) == b._get(i + rs, i + rs + mid)) 
                ll = mid + 1, ad = mid + 1; else rr = mid - 1;
        }
        ans = max(ans, rs * 2 + 1 + ad * 2);
        if (i < n && a.s[i] == a.s[i + 1]) {
            l = 0, r = n, rs = -inf;
            while (l <= r) {
                int mid = (l + r) >> 1;
                if (a.check(i - mid, i + mid + 1)) l = mid + 1, rs = mid; else r = mid - 1;
            }
            ll = 0, rr = n, ad = 0;
            while (ll <= rr) {
                int mid = (ll + rr) >> 1;
                if (a.get(i - rs - 1 - mid, i - rs - 1) == b._get(i + rs + 1, i + rs + 1 + mid)) 
                    ll = mid + 1, ad = mid + 1; else rr = mid - 1;
            }
            ans = max(ans, rs * 2 + 2 + ad * 2);
        }
    }

    F(i, 1, n) {
        int l = 0, r = n, rs = -inf;
        while (l <= r) {
            int mid = (l + r) >> 1;
            if (b.check(i - mid, i + mid)) l = mid + 1, rs = mid; else r = mid - 1;
        }
        int ll = 0, rr = n, ad = 0;
        while (ll <= rr) {
            int mid = (ll + rr) >> 1;
            if (a.get(i - rs - mid, i - rs) == b._get(i + rs + 1, i + rs + mid + 1)) 
                ll = mid + 1, ad = mid + 1; else rr = mid - 1;
        }
        ans = max(ans, rs * 2 + 1 + ad * 2);
        if (i < n && b.s[i] == b.s[i + 1]) {
            l = 0, r = n, rs = -inf;
            while (l <= r) {
                int mid = (l + r) >> 1;
                if (b.check(i - mid, i + mid + 1)) l = mid + 1, rs = mid; else r = mid - 1;
            }
            // if (i == 2) cerr << rs;
            ll = 0, rr = n, ad = 0;
            while (ll <= rr) {
                int mid = (ll + rr) >> 1;
                if (a.get(i - rs - mid, i - rs) == b._get(i + rs + 2, i + rs + 2 + mid)) 
                    ll = mid + 1, ad = mid + 1; else rr = mid - 1;
            }
            ans = max(ans, rs * 2 + 2 + ad * 2);
        }
    }
    
    cout << ans;
    return 0;
}