ICL 2013

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <cmath>
#include <ctime>
#include <cassert>

using namespace std;

#define pb push_back
#define mp make_pair
#define sz(A) (int)(A).size()

typedef long long LL;
typedef long double LD;

const int MOD = int(1e12 + 7), P = 239017, L = int(1e5 + 5);

int len, pos_ans[4], add_right[4], out[4];
char s[2][L], ans[4][2][L];
LL p[L], h[2][L], rh[2][L];

void precalc() {
    for (int k = 0; k < 4; k++)
        for (int i = 0; i < 2; i++)
            for (int j = 0; j < len; j++)
                ans[k][i][j] = '.';

    p[0] = 1;
    for (int i = 1; i < L; i++)
        p[i] = (p[i - 1] * P) % MOD;

    for (int j = 0; j < 2; j++) {
        h[j][0] = s[j][0];
        for (int i = 1; i < len; i++)
            h[j][i] = (h[j][i - 1] * P + s[j][i]) % MOD;
    }

    for (int j = 0; j < 2; j++) {
        rh[j][len - 1] = s[j][len - 1];
        for (int i = len - 2; i >= 0; i--)
            rh[j][i] = (rh[j][i + 1] * P + s[j][i]) % MOD;
    }
}

LL count_hash(int num, int l, int r) {
    if (!l)
        return h[num][r];
    LL val = h[num][r] - h[num][l - 1] * p[r - l + 1];
    if (val < 0)
        val += MOD;
    val %= MOD;
    return val;
}

LL count_rev_hash(int num, int l, int r) {
    LL val = rh[num][l] - rh[num][r + 1] * p[r - l + 1];
    if (val < 0)
        val += MOD;
    val %= MOD;
    return val;
}

int main()
{
//  freopen(".in", "r", stdin);
//  freopen(".out", "w", stdout);

    scanf("%d\n", &len);
    gets(s[0]);
    gets(s[1]);

    precalc();

    // odd, center in the first row
    int l = 0, r = len;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        bool ok = 0;
        for (int i = mid; i < len; i++) {
            int l_ = 0, r_ = mid + 1;
            while (l_ + 1 < r_) {
                int mid_ = (l_ + r_) / 2;
                if (count_hash(0, i + 1, i + mid_) == count_rev_hash(0, i - mid_, i - 1))
                    l_ = mid_;
                else
                    r_ = mid_;
            }
//          if (i == 3)
//              cerr << count_rev_hash(0, i - mid, i - l_ - 1) << " " << count_hash(1, i + l_, i + mid - 1) << endl;

            int rest = mid - l_;
            if (count_rev_hash(0, i - mid, i - l_ - 1) == count_hash(1, i + l_, i + mid - 1)) {
                ok = 1;
                pos_ans[0] = i;
                add_right[0] = l_;
                break;
            }
        }
        if (ok)
            l = mid;
        else
            r = mid;
    }

    out[0] = 2 * l + 1;
    for (int i = pos_ans[0] - l; i <= pos_ans[0] + add_right[0]; i++)
        ans[0][0][i] = s[0][i];
    for (int i = pos_ans[0] + add_right[0]; i < pos_ans[0] + l; i++)
        ans[0][1][i] = s[1][i];

    l = 0, r = len;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        bool ok = 0;
        for (int i = 0; i + mid < len; i++) {
            int l_ = 0, r_ = mid + 1;
            while (l_ + 1 < r_) {
                int mid_ = (l_ + r_) / 2;
                if (count_hash(1, i + 1, i + mid_) == count_rev_hash(1, i - mid_, i - 1))
                    l_ = mid_;
                else
                    r_ = mid_;
            }
//          if (i == 3)
//              cerr << count_rev_hash(0, i - mid, i - l_ - 1) << " " << count_hash(1, i + l_, i + mid - 1) << endl;

            int rest = mid - l_;
            if (count_rev_hash(0, i - mid + 1, i - l_) == count_hash(1, i + l_ + 1, i + mid)) {
                ok = 1;
                pos_ans[1] = i;
                add_right[1] = l_;
                break;
            }
        }
        if (ok)
            l = mid;
        else
            r = mid;
    }

    out[1] = 2 * l + 1;
    for (int i = pos_ans[1] - l + 1; i <= pos_ans[1] - add_right[1]; i++)
        ans[1][0][i] = s[0][i];
    for (int i = pos_ans[1] - add_right[1]; i <= pos_ans[1] + l; i++)
        ans[1][1][i] = s[1][i];

    l = 0, r = len + 1;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        bool ok = 0;
        for (int i = mid - 1; i < len; i++) {
            int l_ = 0, r_ = mid + 1;
            while (l_ + 1 < r_) {
                int mid_ = (l_ + r_) / 2;
                if (count_hash(0, i + 1, i + mid_) == count_rev_hash(0, i - mid_ + 1, i))
                    l_ = mid_;
                else
                    r_ = mid_;
            }

            int rest = mid - l_;
            if (count_rev_hash(0, i - mid + 1, i - l_) == count_hash(1, i + l_, i + mid - 1)) {
                ok = 1;
                pos_ans[2] = i;
                add_right[2] = l_;
                break;
            }
        }
        if (ok)
            l = mid;
        else
            r = mid;
    }

//  printf("%d\n", 2 * l);
    out[2] = 2 * l;
    for (int i = pos_ans[2] - l + 1; i <= pos_ans[2] + add_right[2]; i++)
        ans[2][0][i] = s[0][i];
    for (int i = pos_ans[2] + add_right[2]; i < pos_ans[2] + l; i++)
        ans[2][1][i] = s[1][i];
//  for (int i = 0; i < 2; i++, printf("\n"))
//      for (int j = 0; j < len; j++)
//          printf("%c", ans[2][i][j]);

    // even, center in the second row

    l = 0, r = len + 1;
    while (l + 1 < r) {
        int mid = (l + r) / 2;
        bool ok = 0;
        for (int i = 0; i + mid <= len; i++) {
            int l_ = 0, r_ = mid + 1;
            while (l_ + 1 < r_) {
                int mid_ = (l_ + r_) / 2;
                if (count_hash(1, i, i + mid_ - 1) == count_rev_hash(1, i - mid_, i - 1))
                    l_ = mid_;
                else
                    r_ = mid_;
            }

            int rest = mid - l_;
            if (count_rev_hash(0, i - mid + 1, i - l_) == count_hash(1, i + l_, i + mid - 1)) {
                ok = 1;
                pos_ans[3] = i;
                add_right[3] = l_;
                break;
            }
        }
        if (ok)
            l = mid;
        else
            r = mid;
    }

    out[3] = 2 * l;
    for (int i = pos_ans[3] - l + 1; i <= pos_ans[3] - add_right[3]; i++)
        ans[3][0][i] = s[0][i];
    for (int i = pos_ans[3] - add_right[3]; i <= pos_ans[3] + l - 1; i++)
        ans[3][1][i] = s[1][i];

    int mx = -1, ind = -1;
    for (int i = 0; i < 4; i++)
        if (out[i] > mx) {
            mx = out[i];
            ind = i;
        }

    printf("%d\n", mx);

    for (int i = 0; i < 2; i++, printf("\n"))
        for (int j = 0; j < len; j++)
            printf("%c", ans[ind][i][j]);
        return 0;
}