/////home/mohammed/.config/sublime-text-3/Packages/User

/*input

*/
#include <bits/stdc++.h>
#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
#include <numeric>
#include <math.h>
#include <sstream>
#include <iterator>
#include <cstdlib>
#include <unordered_map>
#include <map>
#include <list>
#include <set>

using namespace std;
using bin = std::bitset<8>;

#define endl ("\n")
#define pi (3.141592653589)
#define mod 1000000007
#define int int64_t
#define float double
#define ll long long
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(c) c.begin(), c.end()
#define min3(a, b, c) min({a,b,c})
#define max3(a, b, c) max({a,b,c})
#define min4(a, b, c, d) min({a,b,c,d})
#define max4(a, b, c, d) max({a,b,c,d})
#define rrep(i, n) for(int i=n-1;i>=0;i--)
#define rep(i,n) for(int i=0;i<n;i++)
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr)
#define ld long double
#define scanArray(a,n) for(int i = 0; i < n; i++){cin >> a[i];}
#define coutArray(a,n) for(int i = 0; i < n; i++){cout << a[i] << " ";};cout << endl;
#define input(type, n) type n; cin>>n;



struct debugger
{
	template<typename T> debugger& operator , (const T& v)
	{
		cerr << v << " ";
		return *this;
	}
} dbg;

bool check_key(map<int, int> m, int key)
{
	if (m.find(key) == m.end())
		return false;

	return true;
}


vector<int> SieveOfEratosthenes(int n)
{
	bool prime[n + 1];
	memset(prime, true, sizeof(prime));


	vector<int> res;
	for (int p = 2; p * p <= n; p++)
	{
		if (prime[p] == true)
		{
			for (int i = p * p; i <= n; i += p)
				prime[i] = false;
		}
	}

	for (int p = 2; p <= n; p++)
		if (prime[p])
			res.push_back(p);
	//cout << p << " ";
	return res;
}

// function to convert decimal to binary
bin decToBinary(int n)
{
	// array to store binary number
	int binaryNum[32];

	// counter for binary array
	int i = 0;
	while (n > 0) {

		// storing remainder in binary array
		binaryNum[i] = n % 2;
		n = n / 2;
		i++;
	}
	string x = "";
	// printing binary array in reverse order
	for (int j = i - 1; j >= 0; j--) {
		x += to_string(binaryNum[j]);
	}
	bin result{x};
	return result;
}
// for example:
// bin result = decToBinary(2);
// bin result2 = decToBinary(10);
// bin z = result xor result2;
// cout << z;
// return 0;
int convertBinaryToDecimal(long long n)
{
	int decimalNumber = 0, i = 0, remainder;
	while (n != 0)
	{
		remainder = n % 10;
		n /= 10;
		decimalNumber += remainder * pow(2, i);
		++i;
	}
	return decimalNumber;
}
int factorial(int n) {

	long long res = 1;
	for (int i = 1; i <= n; i++) {
		res = ((res * i) % mod + mod) % mod ;
	}
	return res;
}





int32_t main()
{
	fast;
#ifndef ONLINE_JUDGE
	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);
#endif

	input(int, t); input(int, k);
	int check[26] = {0};
	int vis[26] = {0};
	rep(_, t) {
		input(char, x);
		check[x - 'a']++;
	}
	bool two = false;
	bool p = false;
	int w = 0;
	int n;
	for (auto i : check) {
		if (i != 0 && i % k == 0) {
			p = true;
		} else if (i != 0 && i < k) {
			cout << 3 << endl;
			return 0;
		} else if (i != 0 && i % (k + 1) == 0) {
			two = true;
		} else if (i != 0 && i > k) {
			two = true;
		} else if (i != 0) {
			cout << 3 <<  endl;
			return 0;
		}
	}


	if (!two) {
		string s = "";
		for (int i = 0; i < 26; i++) {
			if (check[i] != 0) {
				rep(e, check[i] / k) {
					s += char(i + 'a');
				}
			}
		}
		cout << 1 << endl;
		rep(i, k) {
			cout << s;
		}
	} else if (two) {
		cout << 2 << endl;
		string l = "";
		string f = "";
		char r;
		for (int i = 0; i < 26; i++) {
			if (check[i] != 0 && check[i] % (k + 1) == 0) {
				rep(e, check[i] / (k + 1)) {
					f += char(i + 'a');
					l += char(i + 'a');
				}
				vis[i] = 1;
			}
		}
		for (int i = 0; i < 26; i++) {
			if (check[i] != 0 && check[i] > k && check[i] % k != 0 && check[i] % (k + 1) != 0 && vis[i] != 1) {
				rep(e, int(check[i] / k )) {
					f += char(i + 'a');
				}
				rep(e, int(check[i] % k)) {
					l += char(i + 'a');
				}
				vis[i] = 1;
			}
		}
		for (int i = 0; i < 26; i++) {
			if (check[i] != 0 && check[i] % k == 0 && vis[i] != 1) {
				rep(e, check[i] / k) {
					f += char(i + 'a');
				}
				vis[i] = 1;
			}
		}
		rep(i, k) {
			cout << f;
		}
		cout << l << endl;

	}



}