#include <string>
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int N = 100005;

int n, ans, t[2][N], g[2][N];
char a[N], b[N];

unsigned long long pre[2][N], nex[2][N], p[N];

unsigned long long get1(unsigned long long *h, int l, int r)
{
    return h[r] - h[l - 1] * p[r - l + 1];
}

unsigned long long get2(unsigned long long *h, int l, int r)
{
    return h[l] - h[r + 1] * p[r - l + 1];
}

void init(unsigned long long *h1, unsigned long long *h2, int *t, int *g)
{
    for(int i = 1; i <= n; ++ i)
    {
        int l = 1, r = i;
        while(l <= r)
        {
            int mid = l + r >> 1;
            if(get1(h1, i - mid, i - 1) == get2(h2, i + 1, i + mid))
                l = mid + 1, t[i] = mid;
            else
                r = mid - 1;
        }

        if(i == n)
            break;

        l = 1, r = i;
        while(l <= r)
        {
            int mid = l + r >> 1;
            if(get1(h1, i - mid + 1, i) == get2(h2, i + 1, i + mid))
                l = mid + 1, g[i] = mid;
            else
                r = mid - 1;
        }
    }
}

bool check(int k)
{
    int m = k / 2;
    for(int i = m + 1; i <= n; ++ i)
        if(t[0][i] >= m || get1(pre[0], i - m, i - 1) == get2(nex[0], i + 1, i + t[0][i]) + get2(nex[1], i + t[0][i], i + m - 1) * p[t[0][i]])
            return true;
    for(int i = n - m; i >= 1; -- i)
        if(t[1][i] >= m || get2(nex[1], i + 1, i + m) == get1(pre[1], i - t[1][i], i - 1) + get1(pre[0], i - m + 1, i - t[1][i]) * p[t[1][i]])
            return true;

    m += k % 2;
    for(int i = 1; i < n; ++ i)
        if(g[0][i] >= m || get1(pre[0], i - m + 1, i) == get2(nex[0], i + 1, i + g[0][i]) + get2(nex[1], i + g[0][i], i + m - 1) * p[g[0][i]])
            return true;
    for(int i = 1; i < n; ++ i)
        if(g[1][i] >= m || get2(nex[1], i + 1, i + m) == get1(pre[1], i - g[1][i] + 1, i) + get1(pre[0], i - m + 2, i - g[1][i] + 1) * p[g[1][i]])
            return true;
    for(int i = 1; i <= n; ++ i)
        if(get1(pre[0], i - m + 1, i) == get2(nex[1], i, i + m - 1))
            return true;
    return false;
}

int main()
{
    scanf("%d", &n);
    scanf("%s", a + 1);
    scanf("%s", b + 1);

    p[0] = 1;
    for(int i = 1; i <= n; ++ i)
    {
        p[i] = p[i - 1] * 131;
        pre[0][i] = pre[0][i - 1] * 131 + a[i];
        pre[1][i] = pre[1][i - 1] * 131 + b[i];
    }
    for(int i = n; i >= 1; -- i)
    {
        nex[0][i] = nex[0][i + 1] * 131 + a[i];
        nex[1][i] = nex[1][i + 1] * 131 + b[i];
    }

    init(pre[0], nex[0], t[0], g[0]);
    init(pre[1], nex[1], t[1], g[1]);

    int l = 1, r = n + 1;
    while(l <= r)
    {
        int mid = l + r >> 1;
        if(check(mid))
            l = mid + 1, ans = mid;
        else
            r = mid - 1;
    }
    printf("%d\n", ans);

    return 0;
}