#include <iostream>
#include <cstdio>
#include <iomanip>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <bitset>
#include <stack>
#include <utility>
#include <numeric>
#include <algorithm>
#include <functional>
#include <cctype>
#include <complex>
#include <string>
#include <sstream>
#include <fstream>
#include <cassert>
using namespace std;

//common

typedef int  i32;
typedef long long i64,ll;
typedef long double ld;

#define BR "\n"
#define ALL(c) (c).begin(),(c).end()
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define FOR(i,l,r) for(int i=(int)l;i<(int)(r);++i)
#define EACH(it,o) for(auto it = (o).begin(); it != (o).end(); ++it)
#define IN(l,v,r) ((l)<=(v) && (v)<(r))

//config
//#define NDEBUG
//#define INF 1<<30
//#define EPS 1e-8
//const ll MOD =100000007;

//debug
#ifdef NDEBUG
#define DUMP(x)
#define DUMPLN(x)
#define DEBUG(x)
#define DEBUGLN(x)
#define LINE()
#define LINELN()
#define CHECK(exp,act)
#define STOP(e)
#else
#define DUMP(x)  cerr << #x << " = " << (x)
#define DUMPLN(x)  DUMP(x) <<endl
#define DEBUG(x) DUMP(x) << LINE() << " " << __FILE__
#define DEBUGLN(x) DEBUG(x)<<endl
#define LINE()    cerr<< " (L" << __LINE__ << ")"
#define LINELN()    LINE()<<endl
#define CHECK(exp,act)  if(exp!=act){DUMPLN(exp);DEBUGLN(act);}
#define STOP(e)  CHECK(e,true);if(!(e)) exit(1);
#endif

template<class T> inline string toString(const vector<T>& x) {
	stringstream ss;
	REP(i,x.size()){
		if(i!=0)ss<<" ";
		ss<< x[i];
	}
	return ss.str();
}

template<class T> inline string toString(const vector<vector<T> >& map) {
	stringstream ss;
	REP(i,map.size()){
		if(i!=0)ss<<BR;
		ss<< toString(map[i]);
	}
	return ss.str();
}
template<class K,class V>  string toString(map<K,V>& x) {
	string res;stringstream ss;
	for(auto& p:x)ss<< p.first<<":" << p.second<<" ";
	return ss.str();
}

string BITtoString(int bit){
    stringstream ss;
    while(bit!=0){ss<<(bit%2);bit/=2;}
    string res=ss.str();reverse(ALL(res));
    return res;
}

template<typename T,typename V> inline T pmod(T v,V MOD){
	return (v%MOD+MOD)%MOD;
}
#define nextInt(n) scanf("%d",&n)
#define defInt(n) int n;nextInt(n)
#define nextLong(n) scanf("%lld",&n)
#define defLong(n) ll n;nextLong(n)
#define nextDouble(n) scanf("%lf",&n)

template < class BidirectionalIterator >
bool next_combination ( BidirectionalIterator first1 ,
  BidirectionalIterator last1 ,
  BidirectionalIterator first2 ,
  BidirectionalIterator last2 )
{
  if (( first1 == last1 ) || ( first2 == last2 )) {
    return false ;
  }
  BidirectionalIterator m1 = last1 ;
  BidirectionalIterator m2 = last2 ; --m2;
  while (--m1 != first1 && !(* m1 < *m2 )){
  }
  bool result = (m1 == first1 ) && !(* first1 < *m2 );
  if (! result ) {
    // ?
    while ( first2 != m2 && !(* m1 < * first2 )) {
      ++ first2 ;
    }
    first1 = m1;
    std :: iter_swap (first1 , first2 );
    ++ first1 ;
    ++ first2 ;
  }
  if (( first1 != last1 ) && ( first2 != last2 )) {
    // ?
    m1 = last1 ; m2 = first2 ;
    while (( m1 != first1 ) && (m2 != last2 )) {
      std :: iter_swap (--m1 , m2 );
      ++ m2;
    }
    // ?
    std :: reverse (first1 , m1 );
    std :: reverse (first1 , last1 );
    std :: reverse (m2 , last2 );
    std :: reverse (first2 , last2 );
  }
  return ! result ;
}
 
template < class BidirectionalIterator >
bool next_combination ( BidirectionalIterator first ,
  BidirectionalIterator middle ,
  BidirectionalIterator last )
{
  return next_combination (first , middle , middle , last );
}

class Main{
	public:

	int fact(int N){
		int res=1;
		for(int i=1;i<=N;i++)res*=i;
		return res;
	}
	void run(){
		// ifstream cin("D2");
//		ofstream cout( "D2.out" );
		
		while(true){
			int N;cin >> N;if(N==0)break;
			vector<string> ss(N);REP(i,N)cin >> ss[i];

			map<char,int> ctoi;
			map<int,char> itoc;
			int c=0;
			REP(i,N)REP(j,ss[i].size())if(!ctoi.count(ss[i][j])){
				ctoi[ss[i][j]]=c;itoc[c]=ss[i][j];c++;
			}
			vector<int> val(c);
			REP(i,N-1)REP(j,ss[i].size()){
				val[ctoi[ss[i][j]]]+=pow(10,ss[i].size()-1-j);
			}
			vector<int> rst(c);
			REP(j,ss[N-1].size())rst[ctoi[ss[N-1][j]]]+=pow(10,ss[N-1].size()-1-j);
			
			vector<bool> can0(c,true);
			REP(i,N)if(ss[i].size()>=2)can0[ctoi[ss[i][0]]]=false;
			int res=0;
			
			// DUMP(toString(val));
			// DUMP(toString(can0));
			// DUMP(toString(rst));
			
			vector<int> per(10);REP(i,10)per[i]=i;
			do{
				if(per[0]<c && !can0[per[0]])continue;
				int vals=0;REP(i,10)if(per[i]<c)vals+=val[per[i]]*i;
				int rsts=0;REP(i,10)if(per[i]<c)rsts+=rst[per[i]]*i;
				if(vals==rsts)res++;
			}while(next_permutation(ALL(per)));
			res/=fact(10-c);
			cout <<res <<endl;
		}
	}


};
int main(){
	cout <<fixed<<setprecision(15);	
	ios::sync_with_stdio(false);
	Main().run();
	return 0;
}

Measured memory_bytes: 1260