#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <climits>
#include <cstring>
#include <cassert>
#include <unordered_set>


using namespace std;
#define SZ(x) (int)(x.size())
#define REP(i, n) for(int i=0;i<n;++i)
#define FOR(i, a, b) for(int i=a;i<b;++i)
#define RREP(i, n) for(int i=n-1;i>=0;--i)
#define RFOR(i, a, b) for(int i=b-1;i>=a;--i)

#define all(x) begin(x),end(x)
#define dump(x) cerr<<#x<<" = "<<(x)<<endl
#define debug(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<< endl;

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using P = pair<int, int>;
const double eps = 1e-8;
const ll MOD = 1000000007;
const int INF = INT_MAX / 2;
const ll LINF = LLONG_MAX / 2;

template<class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}


template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> p) {
    os << p.first << ":" << p.second;
    return os;
}

template<class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "[";
    REP(i, SZ(v)) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "]";
}

template<class T1, class T2>
ostream &operator<<(ostream &os, const map<T1, T2> &mp) {
    os << "[";
    for (auto it = mp.begin(); it != mp.end(); ++it) {
        if (it != mp.begin()) {
            os << ", ";
        }
        os << *it;
    }
    return os << "]";
}

// edit

bool solve() {
    int n;
    cin >> n;
    if (n == 0) return false;
    vector<string> s(n);
    REP(i, n) cin >> s[i];

    set<vector<int>> st;
    vector<int> d(10);
    iota(all(d), 0);

    vector<char> var;
    for (auto e : s) {
        for (auto c : e) {
            var.push_back(c);
        }
    }
    sort(all(var));
    var.erase(unique(all(var)), var.end());

//    vector<int> var(256, -1);
//    for (auto e : s) {
//        for (auto c : e) {
//            var[c] = 0;
//        }
//    }
    vector<int> coef(256);
    set<char> top;
    for (int i = 0; i < n; ++i) {
        if (s[i].size() > 1) {
            top.insert(s[i][0]);
        }
        int base = 1;
        for (int j = SZ(s[i]) - 1; j >= 0; --j) {
            if (i + 1 != n) {
                coef[s[i][j]] += base;
            } else {
                coef[s[i][j]] -= base;
            }
            base *= 10;
        }
    }


//    set<ll> checked;
    set<ll> accepted;
    int ans = 0;

    vector<int> val(256); // 使い回す
    do {
        ll hash = 1;
        bool ng = false;
        for (int i = 0; i < var.size(); ++i) {
            val[var[i]] = d[i];
            hash *= 10;
            hash += d[i];
            if (d[i] == 0 && top.count(var[i])) {
                ng = true;
            }
        }

//        if (checked.count(hash)) {
//            continue;
//        }
//        checked.insert(hash);
        if (ng) continue;
//        cout << d << endl;

        int sum = 0;
        for (int i = 0; i < var.size(); ++i) {
            int x = val[var[i]] * coef[var[i]];
            sum += x;
        }
        if (sum == 0) {
            accepted.insert(hash);
            ans++;
        }


//        int sum = 0;
//        int last = 0;
//        for (int i = 0; i < n; ++i) {
//            int x = 0;
//            if (s[i].size() > 1 && val[s[i][0]] == 0) {
//                ng = true;
//                break;
//            }
//            for (int j = 0; j < s[i].size(); ++j) {
//                x *= 10;
//                x += val[s[i][j]];
//            }
//
//            sum += x;
//            last = x;
//
//        }

//        if (sum - last == last) {
////            vector<int> vec(d.begin(), d.begin() + var.size());
////            st.insert(vec);
//            accepted.insert(hash);
//        }
    } while (next_permutation(all(d)));

//    for (auto e : st) {
//        cout << e << endl;
//    }

    ans = accepted.size();
    cout << ans << endl;


    return true;
}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
//    std::ifstream in("input.txt");
//    std::cin.rdbuf(in.rdbuf());

    while (solve());


    return 0;
}



Measured memory_bytes: 4688