#include "iostream"
#include "climits"
#include "list"
#include "queue"
#include "stack"
#include "set"
#include "functional"
#include "algorithm"
#include "string"
#include "map"
#include "unordered_map"
#include "unordered_set"
#include "iomanip"
#include "cmath"
#include "random"
#include "bitset"
#include "cstdio"
#include "numeric"
#include "cassert"

using namespace std;

//const long long int MOD = 1000000007;
const int MOD = 1000000007;
//const int MOD = 998244353;
//const long long int MOD = 998244353;

//long long int N, M, K, H, W, L, R;
int N, M, K, H, W, L, R;

int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);

	while (cin >> N, N) {
		vector<string>s(N);
		for (auto &i : s)cin >> i;
		map<char, int>m;
		for (auto i : s) {
			for (auto j : i)m[j] = 0;
		}
		int cnt = 0;
		for (auto &i : m)i.second = cnt++;
		for (auto &i : s) {
			for (auto &j : i)j = m[j];
		}
		M = m.size();
		vector<int>v(10);
		for (int i = 0; i < 10; i++)v[i] = i;
		int ans = 0;
		do {
			int sum = 0;
			bool flag = true;
			for (int i = 0; i < s.size() - 1; i++) {
				if (s[i].size() > 1 && !v[s[i][0]]) {
					flag = false;
					break;
				}
				int add = 0;
				for (auto j : s[i]) {
					add *= 10;
					add += v[j];
				}
				sum += add;
			}
			int fin = 0;
			if (s.back().size() > 1 && !v[s.back()[0]])flag = false;
			for (auto i:s.back()) {
				fin *= 10;
				fin += v[i];
			}
			if (sum == fin && flag)ans++;
		} while (next_permutation(v.begin(), v.end()));
		for (int i = 1; i <= 10 - m.size(); i++)ans /= i;
		cout << ans << endl;
	}
}

