#include<bits/stdc++.h>
using namespace std;
#define int long long
#define ull unsigned long long
#define pr pair<int, int>
#define pb push_back
#define mid (l + r) / 2
#define ls num << 1
#define rs num << 1 | 1

inline int read() {
    int x = 0, m = 1;
    char ch = getchar();

    while (!isdigit(ch)) {
        if (ch == '-') m = -1;
        ch = getchar();
    }

    while (isdigit(ch)) {
        x = x * 10 + ch - 48;
        ch = getchar();
    }

    return x * m;
}

inline void write(int x) {
    if (x < 0) {
        putchar('-');
        write(-x);
        return;
    }

    if (x >= 10) write(x / 10);
    putchar(x % 10 + '0');
}

char get() {
    char ch = getchar();
    while (ch < 'a' || ch > 'z') ch = getchar();
    return ch;
}

const int N = 1e5 + 5;
const ull Base = 1313131;

char a[N], b[N];
ull H1[N], H2[N], H3[N], Pow[N];

signed main() {
    int n = read();

    for (int i = 1; i <= n; i++) {
        a[i] = get();
    }

    Pow[0] = 1;
    for (int i = 1; i <= n; i++) {
        b[i] = get();
        Pow[i] = Pow[i - 1] * Base;
    }

    auto calc1 = [&](int l, int r) -> ull {
        return H1[r] - H1[l - 1] * Pow[r - l + 1];
    };

    auto calc2 = [&](int l, int r) -> ull {
        return H2[r] - H2[l - 1] * Pow[r - l + 1];
    };

    auto calc3 = [&](int l, int r) -> ull {
        return H3[l] - H3[r + 1] * Pow[r - l + 1];
    };

    auto solve = [&]() -> int {
        for (int i = 1; i <= n; i++) {
            H1[i] = H1[i - 1] * Base + a[i];
            H2[i] = H2[i - 1] * Base + b[i];
        }
        for (int i = n; i >= 1; i--) {
            H3[i] = H3[i + 1] * Base + a[i];
        }
        int Ans = 0;
        for (int i = 1; i <= n; i++) {
            int l = 1, r = min(i, n - i + 1), ans = 1;
            while (l <= r) {
                if (calc3(i - mid + 1, i) == calc1(i, i + mid - 1)) {
                    ans = mid;
                    l = mid + 1;
                }
                else r = mid - 1;
            }
            int res = ans;
            l = 1, r = min(i - res, n - (i + res - 1) + 1), ans = 0;
            while (l <= r) {
                if (calc3(i - res - mid + 1, i - res) == calc2(i + res - 1, i + res + mid - 2)) {
                    ans = mid;
                    l = mid + 1;
                }
                else r = mid - 1;
            }
            Ans = max(Ans, (res + ans) * 2 - 1);
            if (a[i] != b[i]) continue;
            l = 1, r = min(i, n - i + 1), ans = 1;
            while (l <= r) {
                if (calc3(i - mid + 1, i) == calc2(i, i + mid - 1)) {
                    ans = mid;
                    l = mid + 1;
                }
                else r = mid - 1;
            }
            Ans = max(Ans, 2 * ans);
        }
        for (int i = 1; i < n; i++) {
            if (a[i] != a[i + 1]) continue;
            int l = 1, r = min(i, n - i), ans = 1;
            while (l <= r) {
                if (calc3(i - mid + 1, i) == calc1(i + 1, i + mid)) {
                    ans = mid;
                    l = mid + 1;
                }
                else r = mid - 1;
            }
            int res = ans;
            l = 1, r = min(i - res, n - (i + res) + 1), ans = 0;
            while (l <= r) {
                if (calc3(i - res - mid + 1, i - res) == calc2(i + res, i + res + mid - 1)) {
                    ans = mid;
                    l = mid + 1;
                }
                else r = mid - 1;
            }
            Ans = max(Ans, (res + ans) * 2);
        }
        return Ans;
    };

    int ans = solve();
    reverse(a + 1, a + n + 1);
    reverse(b + 1, b + n + 1);
    for (int i = 1; i <= n; i++) swap(a[i], b[i]);
    ans = max(ans, solve());
    write(ans);
    putchar('\n');
}