#include<iostream>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<cstring>

#include<algorithm>

using namespace std;

int read()

{

    int x=,f=;char c=getchar();

    while (c<''||c>'') {if (c=='-') f=-;c=getchar();}

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

    return x*f;

}

#define N 510

#define M 5010

#define lson tree[k].ch[0]

#define rson tree[k].ch[1]

#define lself tree[tree[k].fa].ch[0]

#define rself tree[tree[k].fa].ch[1]

int n,m,s,t,ansx,ansy,v[N+M];

struct edge

{

    int x,y,z;

    bool operator <(const edge&a) const

    {

        return z<a.z;

    }

}e[M];

struct data{int ch[],fa,rev,x;

}tree[N+M];

void up(int k)

{

    tree[k].x=k;

    if (v[tree[lson].x]>v[tree[k].x]) tree[k].x=tree[lson].x;

    if (v[tree[rson].x]>v[tree[k].x]) tree[k].x=tree[rson].x;

}

void rev(int k){if (k) swap(lson,rson),tree[k].rev^=;}

void down(int k){if (tree[k].rev) rev(lson),rev(rson),tree[k].rev=;}

bool isroot(int k){return lself!=k&&rself!=k;}

int whichson(int k){return rself==k;}

void push(int k){if (!isroot(k)) push(tree[k].fa);down(k);}

void move(int k)

{

    int fa=tree[k].fa,gf=tree[fa].fa,p=whichson(k);

    if (!isroot(fa)) tree[gf].ch[whichson(fa)]=k;tree[k].fa=gf;

    tree[fa].ch[p]=tree[k].ch[!p],tree[tree[k].ch[!p]].fa=fa;

    tree[fa].fa=k,tree[k].ch[!p]=fa;

    up(fa),up(k);

}

void splay(int k)

{

    push(k);

    while (!isroot(k))

    {

        int fa=tree[k].fa;

        if (!isroot(fa))

            if (whichson(k)^whichson(fa)) move(k);

            else move(fa);

        move(k);

    }

}

void access(int k){for (int t=;k;t=k,k=tree[k].fa) splay(k),tree[k].ch[]=t,up(k);}

void makeroot(int k){access(k),splay(k),rev(k);}

int findroot(int k){access(k),splay(k);for (;lson;k=lson) down(k);splay(k);return k;}

void link(int x,int y){makeroot(x);tree[x].fa=y;}

void cut(int x,int y){makeroot(x);access(y);splay(y);tree[y].ch[]=tree[x].fa=;up(y);}

int query(int x,int y){makeroot(x);access(y);splay(y);return tree[y].x;}

int gcd(int n,int m){return m==?n:gcd(m,n%m);}

int main()

{

#ifndef ONLINE_JUDGE

    freopen("bzoj1050.in","r",stdin);

    freopen("bzoj1050.out","w",stdout);

    const char LL[]="%I64d\n";

#else

    const char LL[]="%lld\n";

#endif

    n=read(),m=read();

    for (int i=;i<=m;i++)

    e[i].x=read(),e[i].y=read(),e[i].z=read();

    s=read(),t=read();

    sort(e+,e+m+);

    ansx=,ansy=;

    for (int i=;i<=n;i++) v[i]=-;

    for (int i=;i<=m;i++) v[i+n]=e[i].z;

    for (int i=m;i;i--)

    if (e[i].x!=e[i].y)

    {

        if (findroot(e[i].x)==findroot(e[i].y))

        {

            int x=query(e[i].x,e[i].y);

            cut(x,e[x-n].x),cut(x,e[x-n].y);

        }

        link(i+n,e[i].x),link(i+n,e[i].y);

        if (findroot(s)==findroot(t))

        {

            int x=v[query(s,t)];

            if (1ll*x*ansy<1ll*ansx*e[i].z) ansx=x,ansy=e[i].z;

        }

    }

    if (ansx==) cout<<"IMPOSSIBLE";

    else if (ansx%ansy==) cout<<ansx/ansy;

    else cout<<ansx/gcd(ansx,ansy)<<'/'<<ansy/gcd(ansx,ansy);

    return ;

}