#include<iostream>

#include<cstdio>

#include<cstring>

#include<cmath>

using namespace std;

inline int Max(int a,int b){return a>b?a:b;}

void read(int &x){

    static char c=getchar();x=;

    while(c<''||c>'') c=getchar();

    while(''<=c&&c<='') x=x*+(c^),c=getchar();

}

#define N 20005

inline int M(int x){return x<?x:x-;}

int n,rt,sum,ans,tot,mxd[N],siz[N],dis[N],ra[N],rb[];bool vis[N];

int cnt,hd[N],nxt[N<<],ed[N],poi[N<<],val[N<<];

void adde(int x,int y,int v){

    nxt[ed[x]]=++cnt; hd[x]=hd[x]?hd[x]:cnt;

    ed[x]=cnt; poi[cnt]=y; val[cnt]=v;

}

void getrt(int x,int fa){

    siz[x]=; mxd[x]=;

    for(int i=hd[x];i;i=nxt[i]){

        int to=poi[i];

        if(to==fa||vis[to]) continue;

        getrt(to,x);

        siz[x]+=siz[to];

        mxd[x]=Max(mxd[x],siz[to]);

    }mxd[x]=Max(mxd[x],sum-siz[x]);

    if(mxd[x]<mxd[rt]) rt=x;

}

void getdis(int x,int fa){

    ra[++ra[]]=dis[x];

    for(int i=hd[x];i;i=nxt[i]){

        int to=poi[i];

        if(to==fa||vis[to]) continue;

        dis[to]=M(dis[x]+val[i]);

        getdis(to,x);

    }

}

void calc(int x){

    rb[]=;

    for(int i=hd[x];i;i=nxt[i]){

        int to=poi[i];

        if(vis[to]) continue;

        ra[]=; dis[to]=val[i];

        getdis(to,x);

        for(int i=ra[];i;--i)

            ans+=rb[ra[i]?-ra[i]:];

        for(int i=ra[];i;--i) ++rb[ra[i]];

    }rb[]=rb[]=rb[]=;

}

void solve(int x){

    vis[x]=; calc(x);

    for(int i=hd[x];i;i=nxt[i]){

        int to=poi[i];

        if(vis[to]) continue;

        sum=siz[to]; rt=;

        getrt(to,x); solve(rt);

    }

}

int gcd(int a,int b){return b?gcd(b,a%b):a;}

int main(){

    read(n); register int i; int q1,q2,q3;

    for(i=;i<n;++i){

        read(q1),read(q2),read(q3); q3%=;

        adde(q1,q2,q3); adde(q2,q1,q3);

    }mxd[rt=]=n+; sum=n; getrt(,); solve(rt);

    ans=ans*+n; tot=n*n;

    int g=gcd(ans,tot); ans/=g; tot/=g;

    printf("%d/%d",ans,tot);

    return ;

}