#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> pi;
#define fi first
#define se second 
#define V vector
#define pb push_back
typedef long long LL;

const LL mod = 444445555566666677;
const LL base = 2333;
const int N = 1e6 + 20;

typedef uint64_t ull;
struct H {
	ull x; H(ull x=0) : x(x) {}
	H operator+(H o) { return x + o.x + (x + o.x < x); }
	H operator-(H o) { return *this + ~o.x; }
	H operator*(H o) { auto m = (__uint128_t)x * o.x;
		return H((ull)m) + (ull)(m >> 64); }
	ull get() const { return x + !~x; }
	bool operator==(H o) const { return get() == o.get(); }
	bool operator<(H o) const { return get() < o.get(); }
};

H pbs[N];
H mul(H a, H b) {
    return a * b;
}

int deal(int n, string a, string b, int prev_ans) {
    int ans = prev_ans;
    V<H> prea(n + 1);
    V<H> preb(n + 1);
    for(int i = 1; i <= n; i++) {
        prea[i] = mul(prea[i - 1], base) + a[i];
        preb[i] = mul(preb[i - 1], base) + b[i];
    }
    auto hasha = [&](int l, int r) -> H {
        assert(r >= l);
        return prea[r] - mul(prea[l - 1], pbs[r - l + 1]);
    };
    auto hashb = [&](int l, int r) -> H {
        assert(r >= l);
        return preb[r] - mul(preb[l - 1], pbs[r - l + 1]);
    };
    auto is_1 = [&](int l, int r, int k) -> bool {
        assert(r >= l);
        if(r + k > n) return 0;
        return hasha(l, r) == hasha(l + k, r + k);
    };
    auto is_2 = [&](int l, int r, int k) -> bool {
        assert(r >= l);
        if(r + k - 1 > n) return 0;
        return hasha(l, r) == hashb(l + k - 1, r + k - 1);
    };
    for(int k = n; k >= 1; k--) {
        // if(ans >= k * 2) break;
        for(int j = k; j <= n; j += k) {
            if(is_1(j, j, k)) {
                int l = 0, r = j;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_1(mid, j, k)) r = mid;
                    else l = mid;
                }
                int L1 = r;

                l = j, r = n + 1;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_1(j, mid, k)) l = mid;
                    else r = mid;
                }
                int R1 = l;

                //1 -> 2? 

                l = R1, r = n + 1;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_2(R1 + 1, mid, k)) l = mid;
                    else r = mid;
                }

                int R2 = l;

                if(R2 - L1 + 1 >= k) {
                    ans = max(ans, 2 * k);
                }
            }
            if(is_2(j, j, k)) {
                int l = 0, r = j;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_2(mid, j, k)) r = mid;
                    else l = mid;
                }
                int L2 = r;

                l = j, r = n + 1;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_2(j, mid, k)) l = mid;
                    else r = mid;
                }
                int R2 = l;

                //1 -> 2? 

                l = 0, r = L2;
                while(l != r - 1) {
                    int mid = l + r >> 1;
                    if(is_1(mid, L2 - 1, k)) r = mid;
                    else l = mid;
                }

                int L1 = r;

                if(R2 - L1 + 1 >= k) {
                    ans = max(ans, 2 * k);
                }

            }
        }
    }
    return ans;
}   
void solve() {
    int n; cin >> n;
    string a, b; cin >> a >> b;
    a = " " + a, b = " " + b;
    int ans = deal(n, a, b, 0);
    reverse(a.begin() + 1, a.end());
    reverse(b.begin() + 1, b.end());
    ans = max(ans, deal(n, b, a, ans));
    cout << ans << endl;
}
int main() {
    pbs[0] = 1;
    for(int i = 1; i < N; i++) pbs[i] = mul(base, pbs[i - 1]);
    ios::sync_with_stdio(0), cin.tie(0);
    // int t; cin >> t;
    // while(t--) 
    solve();
}