#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int,ll>
#define fi first
#define in inline
#define se second
#define mp make_pair
#define pb push_back
#define db double
const int N = 1e6+10;

ll read(){
	ll x = 0,f = 1;char c = getchar();
	for(;c < '0' || c > '9';c = getchar())if(c == '-')f = -1;
	for(;c >= '0' && c <= '9';c = getchar())x = (x<<1) + (x<<3) + c-'0';
	return x * f;
}


int n;
char c[N];
deque<int>s[17576];
vector<pii>change;
int F(int x,int y,int z){return (x - 'a') + 26 * (y - 'a') + 26 * 26 * (z - 'a');}

struct node{
	int nx,pre;
}a[N];

int main(){
	n = read();
	scanf("%s",c + 1);
	for(int i = 1;i + 2 <= n;i++)s[F(c[i],c[i + 1],c[i + 2])].push_back(i);
	int mx = 0,ans = 0;
	for(int i = 1;i <= n;i++)a[i].pre = i-1,a[i].nx = i+1;
	a[n].nx = 0;
	for(int x = 'a';x <= 'z';x++)
		for(int y = 'a';y <= 'z';y++)
			for(int z = 'a';z <= 'z';z++){
				int i = F(x,y,z);
				change.clear();
				int sum = 0;
				while(!s[i].empty()){
					sum++;
					int x = s[i].front();s[i].pop_front();
					int x1 = a[x].nx;int x2 = a[x1].nx;
					int x3 = a[x2].nx;int x4 = a[x3].nx;
					int p1 = a[x].pre;int p2 = a[p1].pre;
					//p2 p1 x x1 x2 x3 x4
					if(!s[i].empty() && s[i].front() == x1)s[i].pop_front();
					if(!s[i].empty() && s[i].front() == x2)s[i].pop_front();
					a[p1].nx = x3,a[x3].pre = p1,change.pb({p1,x3});
					a[0].nx = a[0].pre = 0;
					if(p2 && p1 && x3 && F(c[p2],c[p1],c[x3]) == i)s[i].push_front(p2);
					if(p1 && x3 && x4 && F(c[p1],c[x3],c[x4]) == i)s[i].push_front(p1);
				}
				for(auto it : change)a[it.fi].nx = it.fi + 1,a[it.se].pre = it.se - 1;
				a[0].nx = a[0].pre = 0;
				if(sum > mx)mx = sum,ans = i;		
			}
		
	printf("%d\n",mx);
	int x1 = ans % 26,x2 = ans / 26 % 26,x3 = ans / 26 / 26;
	cout<<char(x1 + 'a')<<char(x2 + 'a')<<char(x3 + 'a')<<endl;

	return 0;

}