#include<iostream>

#include<stdio.h>

#include<string>

#define MAXN 60

using namespace std;

int max_clique(int n, int * * mat, int *ret) ;

int main()

{

    //freopen("acm.acm","r",stdin);

    int i;

    int ans;

    int j;

    string s;

    int num;

    int * * _m;

    int * ret;

    while(cin>>num)

    {

        if(num == )

            break;

        _m = new int * [num];

        ret = new int[num];

        for(i = ; i < num; ++ i)

        {

            _m[i] = new int[num];

            memset(_m[i],,sizeof(int)*num);

        }

    //for(i = 0; i < num; ++ i)

    //        for(j = 0; j < num; ++ j)

    //            cout<<_m[i][j]<<" ";

        for(i = ; i < num; ++ i)

        {

            cin>>s;

            if(s.length() == )

                continue;

            else

            {

                for(j = ; j < s.length(); ++ j)

                {

                    _m[s[] - 'A'][s[j] - 'A'] = ;

                }

            }

        }

    ans = max_clique(num,_m,ret);

    cout<<ans;

    if(ans == )

        cout<<" channel needed."<<endl;

    else

        cout<<" channels needed."<<endl;

    delete [] _m;

    delete ret;

    }

}

void clique(int n, int* u, int * * mat, int size, int& max, int& bb, int * res, int* rr, int* c) {

    int i, j, vn, v[MAXN];

    if (n) {

        if (size + c[u[]] <= max) return;

        for (i = ; i < n + size - max && i < n; ++ i) {

            for (j = i + , vn = ; j < n; ++ j)

                if (mat[u[i]][u[j]])

                    v[vn ++] = u[j];

            rr[size] = u[i];

            clique(vn, v, mat, size + , max, bb, res, rr, c);

            if (bb) return;

        }

    } else if (size > max) {

        max = size;

        for (i = ; i < size; ++ i)

            res[i] = rr[i];

        bb = ;

    }

}

int max_clique(int n, int * *mat, int * ret) {

    int max = , bb, c[MAXN], i, j;

    int vn, v[MAXN], rr[MAXN];

    for (c[i = n - ] = ; i >= ; -- i) {

        for (vn = , j = i + ; j < n; ++ j)

            if (mat[i][j])

                v[vn ++] = j;

        bb = ;

        rr[] = i;

        clique(vn, v, mat, , max, bb, ret, rr, c);

        c[i] = max;

    }

    return max;

}