#include<stdio.h>
#include<string.h>

int N,c2n[40],nf[15],p,len[15];
char S[15][15],ch[15];

int s2i(char *s)
{
	int res=c2n[s[0]-'A'],i;
	if(strlen(s)>1&&res==0)return -1;
	for(i=1;s[i];i++)
	{
		res*=10;
		res+=c2n[s[i]-'A'];
	}
	return res;
}

int check()
{
	int p=len[N-1],i,j,c,t;
	char *a=S[N-1];
	if(len[N-1]!=0&&c2n[S[N-1][0]-'A']==0)return -1;
	for(i=c=0;p>=0&&c2n[a[p]-'A']!=-1;p--,i++)
	{
		for(j=t=0;j<N-1;j++)
			if(len[j]>=i)
			{
				if(len[j]!=0&&c2n[S[j][0]-'A']==0)return-1;
				if(c2n[S[j][len[j]-i]-'A']==-1)return 0;
				t+=c2n[S[j][len[j]-i]-'A'];
			}
		if((t+c)%10!=c2n[a[p]-'A'])
			return -1;
		c=(t+c)/10;
	}
	return p<0&&c==0?1:0;
}

int dfs(int d)
{
	int res=0,tmp,t,i;
	tmp=check();
	if(tmp==1)
	{
		return 1;
	}
	if(tmp==-1)
		return 0;
	t=0;
	for(i=0;i<10;i++)
	{
		if(nf[i]==0)
		{
			nf[i]=1;
			c2n[ch[d]-'A']=i;
			res+=dfs(d+1);
			c2n[ch[d]-'A']=-1;
			nf[i]=0;
		}
	}
	return res;
}

int main()
{
	int i,j,k;
	for(;scanf("%d\n",&N),N;)
	{
		p=0;
		memset(ch,0,sizeof(ch));
		memset(c2n,-1,sizeof(c2n));
		memset(nf,0,sizeof(nf));
		for(i=0;i<N;i++)
		{
			gets(S[i]);
			len[i]=strlen(S[i])-1;
		}
		for(i=0;i<N;i++)if(len[i]>len[N-1])break;
		if(i!=N)
		{
			puts("0");
			continue;
		}
		for(i=0;i<10;i++)
			for(j=0;j<N;j++)
			{
				if(len[j]>=i)
				{
					for(k=0;k<p;k++)
						if(ch[k]==S[j][len[j]-i])break;
					if(k==p)
						ch[p++]=S[j][len[j]-i];
				}
			}
			
		printf("%d\n",dfs(0));
	}
	return 0;
}