#include <bits/stdc++.h>

#define ll long long
#define el endl
#define umi unordered_map<int, int>
#define umll unordered_map<ll, ll>
#define all(vect) vect.begin(), vect.end()
#define reset(A) memset(A, true, sizeof(A))
#define approx(n) fixed << setprecision(n)
#define pb push_back

const int mod = 1e9 + 7;

using namespace std;

int n, a[15];
string s[15];
bool check[15];
int minn = INT_MAX;

int ok()
{
    int res = 0;
    for(int i = 1; i < n; i++)
    {
        for(int j = 0; j < s[a[i]].size(); j++)
        {
            for(int k = 0; k < s[a[i + 1]].size(); k++)
            {
                if(s[a[i]][j] == s[a[i + 1]][k])
                    res++;
            }
        }
    }
    return res;
}

void back(int i)
{
    for(int j = 1; j <= n; j++)
    {
        if(check[j])
        {
            a[i] = j;
            check[j] = false;
            if(i == n)
            {
                minn = min(minn, ok());
//              for(int i = 1; i <= n; i++)
//              {
//                  cout << a[i] << " ";
//              }
//              cout << el << el;
//              cout << minn << el;
            }
            else
                back(i + 1);
            check[j] = true;
        }


    }
}

void solve()
{
    reset(check);
    cin >> n;
    minn = 100000;
    for(int i = 1; i <= n; i++)
    {
        cin >> s[i];
    }
    back(1);
    cout << minn << el;
}

int main()
{
    int t = 1;
//  cin >> t;
//  cin.ignore();
    while(t--)
    {
        solve();
    }
    return 0;
}