#include<bits/stdc++.h>
using namespace std;
int n;
string s, t;
int f(char a, char b, char c) {
    return (a - 'a') * 26 * 26 + (b - 'a') * 26 + (c - 'a');
}
const int N = 26 * 26 * 26, M = 1e6 + 5;
vector<int> pos[N];
int nex[M], pre[M];
int main() {
    cin >> n >> s; s = " " + s; t.resize(3);
    for (int i = 1; i <= n - 2; i++) pos[f(s[i], s[i + 1], s[i + 2])].push_back(i);
    int ans1 = -1, ans2 = 0;
    for (int i = 0; i <= n; i++) nex[i] = i + 1;
    nex[n + 1] = n + 1;
    for (int i = 1; i <= n + 1; i++) pre[i] = i - 1;
    for (int i = 0; i < N; i++) {
        if (pos[i].size()) {
            t[2] = 'a' + (i % 26);
            t[1] = 'a' + ((i / 26) % 26);
            t[0] = 'a' + ((i / 26 / 26) % 26);
            vector<int> del;
            int cnt = 0, now = pos[i][0];
            auto check = [&](int x) -> bool {
                if (!x) return 0;
                int y = nex[x], z = nex[y];
                if (y == n + 1 || z == n + 1) return 0;
                if (s[x] == t[0] && s[y] == t[1] && s[z] == t[2]) return 1;
                return 0;
            } ;
            int cur = 0, len = pos[i].size();
            while (1) {
                cnt ++;
                int now2 = nex[now], now3 = nex[now2], nex4 = nex[now3];
                del.push_back(now); del.push_back(now2); del.push_back(now3);
                int pre1 = pre[now], pre2 = pre[pre1];
                nex[pre1] = nex[now3]; pre[nex[now3]] = pre1;
                if (check(pre2)) now = pre2;
                else if (check(pre1)) now = pre1;
                else {
                    while (cur < len && pos[i][cur] < nex4) cur ++;
                    if (cur < len) now = pos[i][cur];
                    else break;
                }
            }
            if (cnt > ans1) {
                ans1 = cnt; ans2 = i;
            }
            for (int v : del) pre[v] = v - 1, nex[v] = v + 1, nex[v - 1] = v, pre[v + 1] = v;
        }
    }
    cout << ans1 << '\n';
    int i = ans2;
    t[2] = 'a' + (i % 26);
    t[1] = 'a' + ((i / 26) % 26);
    t[0] = 'a' + ((i / 26 / 26) % 26);  
    cout << t;
    return 0;
}