#include <bits/stdc++.h>
using namespace std;
int n; string a, b;
constexpr int Ml = 13331, Md = 1e9+7;
constexpr int mul(int x, int y = Ml){return static_cast<long long>(x) * y % Md;}
constexpr int add(int x, int y){x += y;return x >= Md? x - Md : x;}
constexpr int sub(int x, int y){x -= y;return x < 0? x + Md : x;}
int p[100010]{1};
string rev(string s){reverse(s.begin() + 1, s.end());return s;}
int* hsh(string s){int *ret = new int[n + 1]();for (int i = 1; i <= n; ++i)ret[i] = add(mul(ret[i - 1]), s[i]);return ret;}
int hshv(int *hsh, int l, int r){return sub(hsh[r], mul(hsh[l - 1], p[r - l + 1]));}
int hshrv(int *hsh, int l, int r){return hshv(hsh, n - r + 1, n - l + 1);}
template <typename Func_t>int bsch(int L, int R, Func_t func)//last func = true, func:TTT... FFF...
{int ret = L - 1;while (L <= R){int M = L + R >> 1;if (func(M))ret = M, L = M + 1;else R = M - 1;}return ret;}

[[debug]]void print(int ul, int ur, int dl, int dr){cout << endl;
    assert(1 <= ul && ur <= n && dl >= 1 && dr <= n);
    cout << "%" << ul << "-"<< ur << "," << dl << "-" << dr << endl;
    for (int i = 1; i <= n; ++i)cout << (i >= ul && i <= ur? a[i] : '_');cout << endl;
    for (int i = 1; i <= n; ++i)cout << (i >= dl && i <= dr? b[i] : '_');cout << endl;
}

int solud(){
    auto Up = hsh(a), Uprev = hsh(rev(a)), Dwn = hsh(b), Dwnrev = hsh(rev(b)); int ret = 1;
    for (int o : {0, 1})//o+1 Mid,at a_i~a_{i+o}
        for (int i = 1; i + o <= n; ++i)if (a[i] == a[i + o]){
            int Lu = bsch(1, min(i - 1, n - i - o), [&](int Ln){int L = i - Ln, R = i + o + Ln;return hshv(Up, L, R) == hshrv(Uprev, L, R);});
            int Ld = bsch(1, min(i - Lu - 1, n + 1 - i - o - Lu), [&](int L2){
                return hshv(Up, i - Lu - L2, i - Lu - 1) == hshrv(Dwnrev, i + o + Lu, i + o + Lu + L2 - 1);
            });
            //print(i - Lu - Ld, i + o + Lu, i + o + Lu, i + o + Lu + Ld - 1);
            ret = max(ret, (Lu + Ld << 1) + 1 + o);
        }
   // cout << "--" << endl;
    for (int i = 1; i <= n; ++i)if (a[i] == b[i]){//2 Mid, at a_i and b_i
        int L1 = bsch(1, min(i - 1, n - i), [&](int P){
            return hshv(Up, i - P, i) == hshrv(Dwnrev, i, i + P);
        });
        //print(i - L1, i, i, i + L1);
        ret = max(ret, L1 + 1 << 1);
    }
    return ret;
}
int main(){
    ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
    cin >> n >> a >> b; a = " " + a, b = " " + b;
    for (int i = 1; i <= n; ++i)p[i] = mul(p[i - 1]);
    int rs = solud();tie(a, b) = make_pair(rev(b), rev(a));// cout << "-----------------" << endl;
    rs = max(rs, solud()); cout << rs << endl;
    return 0;
}
/*
5
pkusc
pkukp

6


9
abcdeezxv
bnmjkdcba

10


8
abcddcba
reterwyy

8


7
abcdcba
trettyy

7
*/