#include<cstdio>

 #include<cstring>

 #include<algorithm>

 using namespace std;

 const int maxn=;

 struct node

 {

     int x,y,z;

     bool operator < (const node &we)const

     {

         return z<we.z;

     }

 }f[maxn];

 int n,m;

 int father[maxn];

 int getfather(int x)

 {

     if(father[x]==x) return x;

     father[x]=getfather(father[x]);

     return father[x];

 }

 void merging(int x,int y)

 {

     father[getfather(x)]=getfather(y);

 }

 int s,t;

 double ans=1e9;

 int ans1,ans2;

 int gcd(int a,int b)

 {

     return b==?a:gcd(b,a%b);

 }

 int main()

 {

     scanf("%d%d",&n,&m);

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

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

     {

         scanf("%d%d%d",&f[i].x,&f[i].y,&f[i].z);

         merging(f[i].x,f[i].y);

     }

     scanf("%d%d",&s,&t);

     if(getfather(s)!=getfather(t))

     {

         printf("IMPOSSIBLE\n");

         return ;

     }

     sort(f+,f+m+);

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

     {

         for(int k=;k<=n;k++) father[k]=k;

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

         {

             merging(f[j].x,f[j].y);

             if(getfather(s)==getfather(t))

             {

                 double qw=(double)f[j].z/(double)f[i].z;

                 if(qw<ans)

                 {

                     ans=qw;

                     ans1=f[j].z;ans2=f[i].z;

                 }

                 break;

             }

         }

     }

     if(ans1==ans2)

     {

         printf("");

     }

     else

     {

         int we=gcd(ans1,ans2);

         if(ans2/we==) printf("%d",ans1/we);

         else printf("%d/%d\n",ans1/we,ans2/we);

     }

     return ;

 }