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| #include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <cctype>
#include <cmath>
#define ll long long
#define ri register int
using std::sort;
using std::min;
using std::max;
using std::swap;
template <class T>inline void read(T &x){
x=0;int ne=0;char c;
while(!isdigit(c=getchar()))ne=c=='-';
x=c-48;
while(isdigit(c=getchar()))x=(x<<3)+(x<<1)+c-48;
x=ne?-x:x;return ;
}
const int maxm=5005;
const int maxn=505;
const int inf=0x7fffffff;
struct Edge{
int x,y,dis;
bool operator <(const Edge &b)const{
return dis<b.dis;
}
}edge[maxm];
int num_edge=0;
int n,m,s,t;
int fa[maxn];
int get(int x){return fa[x]==x?fa[x]:(fa[x]=get(fa[x]));}
int gcd(int a,int b){
return b?gcd(b,a%b):a;
}
int main(){
int x,y,v,xx,yy;
bool flag=0;
read(n),read(m);
for(ri i=1;i<=m;i++){
read(x),read(y),read(v);
edge[i].x=x,edge[i].y=y,edge[i].dis=v;
}
read(s),read(t);
sort(edge+1,edge+1+m);
int mx,cnt=0;
double mi=inf;
int fz,fm;
for(ri i=1;i<=m;i++){
mx=-inf,flag=0;
for(ri j=1;j<=n;j++)fa[j]=j;
for(ri j=i;j<=m;j++){
x=edge[j].x,y=edge[j].y,v=edge[j].dis;
xx=get(x),yy=get(y);
if(xx==yy)continue;
fa[xx]=yy;
mx=max(mx,v);
if(get(s)==get(t)){
flag=1;break;
}
}
if(i==1&&get(s)!=get(t)){
puts("IMPOSSIBLE");
return 0;
}
else if(flag){
double tmp=(double)mx/edge[i].dis;
if(tmp<mi){
flag=1;
mi=tmp;
fm=edge[i].dis,fz=mx;
}
}
}
int GCD=gcd(fz,fm);
fm=fm/GCD,fz=fz/GCD;
if(fm==1)printf("%d\n",fz);
else printf("%d/%d\n",fz,fm);
return 0;
}
|