#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b)for(int i=a;i<b;i++)
#define repp(x,arr) for(auto& x:arr)
#define ll long long
#define ull unsigned long long
#define int ll
#define db double
#define pb push_back
#define all(v) v.begin(),v.end()
#define F first
#define S second
#define mod 1000000007
#define popcount(x) __builtin_popcountll(x)
#define pll pair<ll,ll>
#define pii pair<int,int>
#define nl "\n"
#define PI 3.1415926536 //acos(-1.0)
#define eps 0.00000001
#define mpp make_pair
#define lb lower_bound
#define ub upper_bound
#define PQ priority_queue<int> //by default provide largest element;
#define RS set <ll, greater <ll> >
#define PQS priority_queue<ll,vector<ll>,greater<ll>>
#define ZERO(a) memset(a,0,sizeof(a))
#define inf 0x3f3f3f3f
using vi = vector<int>;
using vii = vector<pii>;
using vb = vector<bool>;
using vl = vector<ll>;
using vs = vector<string>;
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1}; // for every grid problem!!
const int dxn[8]={0,1,1,1,0,-1,-1,-1},dyn[8]={1,1,0,-1,-1,-1,0,1};
template <typename A, typename B> A amax (A &a, B b){ if (b > a) a = b ; return a; }
template <typename A, typename B> A amin (A &a, B b){ if (b < a) a = b ; return a; }
template <typename A, typename B> A mod1 (A &a, B b){ a=(a%b+b)%b ; return a; }
int M[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
bool isleap(int by){return (by%4==0 && (by%100!=0 || by%400==0));};
inline int gcd(int x,int y){return (y==0)?x:gcd(y,x%y);}
inline int mul(int a, int b) { return (int) ((long long) (a%mod * b%mod) % mod);}
inline int add(int a,int b){return (a%mod+b%mod)%mod;}
inline int sub(int a,int b){return (a-b+mod)%mod;}
inline int binpow(int a,int b){
a%=mod;int res=1;
while(b){if(b&1)res=res*a%mod;a=a*a%mod;b/=2;}
return res;
}
inline int inv(int a){return binpow(a,mod-2)%mod;}
struct trie{
trie*child[26];int cnt=0;bool stop=false;
trie(){
rep(i,0,26)child[i]=NULL;
//cnt=0;
}
};
void insert(const string&s,trie*root){
trie*node=root;
for(auto ch:s){
int id=(ch-'a');
if(!node->child[id]){
node->child[id]=new trie();
}
node=node->child[id];
node->cnt++;
}
node->stop=true;
}
map<trie*,int>d;
void dfs(trie*node){
d[node]=1;
for(int i=0;i<26;i++){
if(!node->child[i])continue;
dfs(node->child[i]);
d[node]=max(d[node],d[node->child[i]]+1);
}
}
string t;
void dfs2(trie*node){
if(node->stop==true)t+='P';
for(int i=0;i<26;i++){
if(!node->child[i])continue;
if(d[node]>d[node->child[i]]+1){
t+=(char)(i+'a');
dfs2(node->child[i]);
}
}
for(int i=0;i<26;i++){
if(!node->child[i])continue;
if(d[node]==d[node->child[i]]+1){
t+=(char)(i+'a');
dfs2(node->child[i]);
}
}
t+='-';
}
void solve(){
int n;cin>>n;
trie*a=new trie();
rep(i,0,n){string s;cin>>s;insert(s,a);}
dfs(a);
dfs2(a);
while(t.back()=='-')t.pop_back();
cout<<t.size()<<nl;
repp(x,t)cout<<x<<nl;
}
int32_t main()
{
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int T=1;//cin >> T;
while(T--)solve();
return 0;
}
