#include <iostream>
#include <iomanip>
#include <vector> 
 
using namespace std;
 
#define forsn(i, s, n) for (int i = int(s); i < int(n); i++)
#define forn(i, n) forsn(i, 0, n)
#define dforsn(i, s, n) for (int i = int(n) - 1; i >= int(s); i--)
#define dforn(i, n) dforsn(i, 0, n)
 
#define sz(x) int(x.size())
#define all(x) begin(x), end(x)
 
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef long double ld;
 
const int ALPHA = 26;
const int INF = 1e9;
 
struct Edge {
    int u, v, w;
    Edge(int a, int b, int c) : u(a), v(b), w(c) {}
};
 
int id(char x, char y) { return (x - 'a') * ALPHA + (y - 'a'); }
 
const int NODES = ALPHA * ALPHA;
 
template<typename T>
void chmax(T &x, T v) {
    if (x < v) x = v;
}
 
template<typename T>
void chmin(T &x, T v) {
    if (x > v) x = v;
}
 
int main() {
    ios::sync_with_stdio(0);                
    cin.tie(0); cout.tie(0);
 
    int n;
    while (cin >> n) {
        if (n == 0) break;
        vector<Edge> graph;
        graph.reserve(n);
        forn(i, n) {
            string s;
            cin >> s;
            int w = sz(s);
            if (w < 2) continue;
            int u = id(s[0], s[1]);
            int v = id(s[w - 2], s[w - 1]);
            graph.push_back(Edge(u, v, w));
        }
        n = sz(graph);
        vector<vi> dp(NODES + 1, vi(NODES, -INF));
        dp[0] = vi(NODES, 0);
        forn(i, NODES) {
            forn(j, n) {
                Edge &e = graph[j];
                if (dp[i][e.u] < 0) continue;
                chmax(dp[i + 1][e.v], dp[i][e.u] + e.w);
            }
        }
        ld x = 0;
        forn(u, NODES) {
            if (dp[NODES][u] < 0) continue;
            ld y = INF;
            forn(i, NODES) {
                if (dp[i][u] < 0) continue;
                chmin(y, (dp[NODES][u] - dp[i][u]) / ld(NODES - i));
            }
            chmax(x, y);
        }
        if (x < 1) {
            cout << "No solution.\n";
        } else {
            cout << fixed << setprecision(2) << x << "\n";
        }
    }
 
    return 0;
}