#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define SZ(x) ((int) (x).size())
#define ALL(a) (a).begin(), (a).end()
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define REP(i, n) for (int i = 0, _n = (n); i < _n; ++i)
#define debug(x) cout << "[" << #x << " = " << (x) << "]" << endl
#define left __left
#define right __right
#define prev __prev
#define next __next
#define fi first
#define se second
template <class X, class Y>
bool maximize(X &x, Y y) {
if (x < y) return x = y, true;
else return false;
}
template <class X, class Y>
bool minimize(X &x, Y y) {
if (x > y) return x = y, true;
else return false;
}
const int ALPHABET_SIZE = 26;
struct Node {
Node* child[ALPHABET_SIZE];
int cnt, high, maxHigh;
Node() {
REP(i, ALPHABET_SIZE) child[i] = nullptr;
cnt = 0;
high = 0, maxHigh = 0;
}
};
typedef Node* node;
#define MAX_NODE 500'500
Node nodes[MAX_NODE + 2];
int trieNode;
Node *root;
Node* createNode() {
return &nodes[trieNode++];
}
void addString(const string &s) {
Node* p = root;
for (char c : s) {
int x = c - 'a';
if (p->child[x] == nullptr) p->child[x] = createNode();
p = p->child[x];
}
p->cnt++;
}
void dfs(Node *u) {
u->maxHigh = u->high;
REP(i, ALPHABET_SIZE) {
if (u->child[i] == nullptr) continue;
u->child[i]->high = u->high + 1;
dfs(u->child[i]);
maximize(u->maxHigh, u->child[i]->maxHigh);
}
}
vector <char> opt;
/// cuoi cung cta chi de lai only one longest word - dont erase;
void calc(Node *u, int c) {
if (c != -1) opt.push_back((char) c + 'a');
if (u->cnt > 0) {
REP(i, u->cnt) opt.push_back('P');
}
REP(i, ALPHABET_SIZE) {
if (u->child[i] == nullptr) continue;
if (u->child[i]->maxHigh != u->maxHigh) {
calc(u->child[i], i);
}
}
REP(i, ALPHABET_SIZE) {
if (u->child[i] == nullptr) continue;
if (u->child[i]->maxHigh == u->maxHigh) {
calc(u->child[i], i);
}
}
opt.push_back('-');
}
int main() {
ios_base::sync_with_stdio(false);cin.tie(nullptr);
// freopen("test.inp","r",stdin);
// freopen("test.out","w",stdout);
root = createNode();
int n; cin >> n;
FOR(i, 1, n) {
string s;
cin >> s;
addString(s);
}
dfs(root);
calc(root, -1);
while (!opt.empty() && opt.back() == '-') opt.pop_back();
cout << SZ(opt) << "\n";
for (char c : opt) cout << c;
return 0;
}
/* Discipline - Calm */
