/**
 * Prof.Nicola
**/
#include <bits/stdc++.h>

using namespace std;
#define endl "\n"
#define mp make_pair
#define F first
#define S second
#define REP(i,l,r) for(long long i=(l);i<(r);i++)
#define PER(i,l,r) for(long long i=(r)-1;i>=(l);i--)
const long dx[4]={1,0,-1,0},dz[4]={0,1,0,-1};
const long double pi=3.14159265359;
const long long mod=1e9+7;
long long p(long long x){while(x&(x-1)){x=x&(x-1);}return x;}
template<class T>void re(T&x){cin>>x;}
template<class T1,class T2> void re(pair<T1,T2>&x){re(x.first);re(x.second);}
template<class T>void re(vector<T>&x){for(long i=0;i<x.size();i++){re(x[i]);}}
template<class T>void re(deque<T>&x){for(long i=0;i<x.size();i++){re(x[i]);}}
template<class T>void out(T x){cout<<x<<" ";}
template<class T1,class T2>void out(pair<T1,T2>x){out(x.first);out(x.second);cout<<endl;}
template<class T>void out(vector<T>x,long l=0,long r=0){if(!r){r=x.size();}for(long i=l;i<r;i++){out(x[i]);}cout<<endl;}
template<class T>void out(deque<T>x,long l=0,long r=0){if(!r){r=x.size();}for(long i=l;i<r;i++){out(x[i]);}cout<<endl;}
template<class T>T cross(complex<T>x,complex<T>z){return (conj(x)*z).imag();}
template<class T>T dot(complex<T>x,complex<T>z){return (conj(x)*z).real();}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    long long n,k;
    char c;
    cin>>n>>k;
    string s,add,t;
    cin>>s;
    bool ok=true;
    vector<long>vis(26);
    REP(i,0,n){
        vis[s[i]-'a']++;
    }
    REP(i,0,26){
        if(vis[i]%k!=0){
            ok=false;
        }
    }
    if(ok){
        cout<<1<<endl;
        REP(i,0,k){
            REP(j,0,26){
                c='a'+j;
                REP(l,0,vis[j]/k){
                    cout<<c;
                }
            }
        }
        return 0;
    }
    REP(i,0,26){
        if((vis[i]%k)>(vis[i]/k)){
            cout<<3<<endl;
            return 0;
        }
    }
    REP(i,0,26){
        c='a'+i;
        REP(j,0,vis[i]%k){
            add+=c;
        }
    }
    t=add;
    REP(i,0,26){
        c='a'+i;
        REP(j,0,(vis[i]/k)-(vis[i]%k)){
            t+=c;
        }
    }
    REP(i,0,k){
        cout<<t;
    }
    cout<<add<<endl;
    return 0;
}