1 #include<cstdio>
  2 #include<cstdlib>
  3 #include<cstring>
  4 #include<iostream>
  5 #include<algorithm>
  6 using namespace std;
  7
  8 const int N=20010;
  9 int n,len,ans;
 10 int v[5],t[5],d[N],first[N],mark[N],size[N];
 11 struct node{
 12     int x,y,d,next;
 13 }a[2*N];
 14
 15 void ins(int x,int y,int d)
 16 {
 17     a[++len].x=x;a[len].y=y;a[len].d=d;
 18     a[len].next=first[x];first[x]=len;
 19 }
 20
 21 int gcd(int x,int y)
 22 {
 23     if(y==0) return x;
 24     return gcd(y,x%y);
 25 }
 26
 27 void find_root(int x,int fa,int tot,int &root)
 28 {
 29     size[x]=1;
 30     bool bk=1;
 31     for(int i=first[x];i;i=a[i].next)
 32     {
 33         int y=a[i].y;
 34         if(y==fa || mark[y]) continue;
 35         find_root(y,x,tot,root);
 36         size[x]+=size[y];
 37         if(2*size[y]>tot) bk=0;
 38     }
 39     if(bk && 2*(tot-size[x])<=tot) root=x;
 40 }
 41
 42 void DFS(int x,int fa)
 43 {
 44     int now=((4-d[x])%4+4)%4;
 45     ans+=v[now];
 46     t[d[x]]++;
 47     size[x]=1;
 48     for(int i=first[x];i;i=a[i].next)
 49     {
 50         int y=a[i].y;
 51         if(mark[y] || y==fa) continue;
 52         d[y]=(d[x]+a[i].d)%4;
 53         DFS(y,x);
 54         size[x]+=size[y];
 55     }
 56 }
 57
 58 void dfs(int x,int tot)
 59 {
 60     find_root(x,0,tot,x);
 61
 62     memset(v,0,sizeof(v));
 63     mark[x]=1;d[x]=0;v[0]++;
 64
 65     for(int i=first[x];i;i=a[i].next)
 66     {
 67         int y=a[i].y;
 68         if(mark[y]) continue;
 69         d[y]=d[x]+a[i].d;
 70         memset(t,0,sizeof(t));
 71         DFS(y,x);
 72         for(int j=0;j<4;j++) v[j]+=t[j];
 73     }
 74     for(int i=first[x];i;i=a[i].next)
 75     {
 76         int y=a[i].y;
 77         if(mark[y]) continue;
 78         dfs(y,size[y]);
 79     }
 80 }
 81
 82 int main()
 83 {
 84     freopen("a.in","r",stdin);
 85     // freopen("czyak.in","r",stdin);
 86     // freopen("czyak.out","w",stdout);
 87     while(1)
 88     {
 89         scanf("%d",&n);
 90         if(!n) break;
 91         ans=0;len=0;
 92         memset(mark,0,sizeof(mark));
 93         memset(first,0,sizeof(first));
 94         for(int i=1;i<n;i++)
 95         {
 96             int x,y,d;
 97             scanf("%d%d%d",&x,&y,&d);
 98             d%=4;
 99             ins(x,y,d);
100             ins(y,x,d);
101         }
102         // for(int i=1;i<=len;i+=2) printf("%d --> %d  %d\n",a[i].x,a[i].y,a[i].d);
103         dfs(1,n);
104         int fz=2*ans+n,fm=n*n;
105         int g=gcd(fz,fm);
106         fz/=g;fm/=g;
107         printf("%d/%d\n",fz,fm);
108     }
109     return 0;
110 }