求助，急急

#include<bits/stdc++.h>
using namespace std;
int f[5005],n,m,r1,r2,a=1e9,b=1e9;
struct dog{
	int x,y,z;
}w[200005];
int find(int x)
{
	if(f[x]==x)	return x;
	return f[x]=find(f[x]);
}
bool cmp(dog x,dog y)
{
	return x.z<y.z;
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=m;i++)
		cin>>w[i].x>>w[i].y>>w[i].z;
	sort(w+1,w+m+1,cmp);
	int s,t;
	cin>>s>>t;
	for(int i=1;i<=m;i++)
	{
		for(int j=1;j<=m;j++)
			f[j]=j;
		for(int j=1;j<=m;j++)
		{
			r1=find(w[j].x);
			r2=find(w[j].y);
			if(r1!=r2)	f[r1]=r2;
			if(find(s)==find(t))
			{
				if(w[j].z*b<a*w[i].z)
				{
					b=w[j].z;
					a=w[i].z;
				}
				break;
			}
		}
	}
	if(a==1e9)
	{
		cout<<"IMPOSSIBLE";
		return 0;
	}
	if(a/__gcd(a,b)==1)	cout<<b/__gcd(a,b);
	else	cout<<b/__gcd(a,b)<<"/"<<a/__gcd(a,b);
	return 0;
}