1 #include<iostream>
2 #include<cstdio>
3 #include<queue>
4 using namespace std;
5 typedef double dd;
6 const int maxn=1007;
7 const int maxm=5007;
8 int n,m,num;
9 dd l,r,mid;
10 dd d[maxn];
11 queue<int>q;
12 dd val[maxn];
13 int cnt[maxn],head[maxn];
14 bool vis[maxn];
15 struct Edge{
16 int next;int to;dd dis;
17 }edge[maxm];
18 void add(int from,int to,dd dis){
19 edge[++num].next=head[from];
20 edge[num].to=to;
21 edge[num].dis=dis;
22 head[from]=num;
23 }
24 bool check(dd mid){
25 for(int i=1;i<=n;i++){
26 q.push(i);d[i]=0;cnt[i]=1;vis[i]=true;
27 }
28 while(!q.empty()){
29 int u=q.front();q.pop();vis[u]=false;
30 for(int i=head[u];i;i=edge[i].next){
31 int v=edge[i].to;
32 if(d[v]>d[u]+(dd)mid*(dd)edge[i].dis-(dd)val[u]){
33 d[v]=d[u]+(dd)mid*(dd)edge[i].dis-(dd)val[u];
34 if(!vis[v]){
35 q.push(v);vis[v]=true;
36 if(++cnt[v]>=n) return 1;
37 }
38 }
39 }
40 }
41 return false;
42 }
43 int main(){
44 cin>>n>>m;
45 for(int i=1;i<=n;i++) cin>>val[i];
46 for(int i=1;i<=m;i++){
47 int u,v,w;cin>>u>>v>>w;
48 add(u,v,w);
49 }
50 r=(dd)maxn*maxm;
51 while(r-l>=1e-4){
52 mid=(double)(l+r)/2;
53 if(check(mid)) l=mid;
54 else r=mid;
55 }
56 printf("%.2lf",l);
57 return 0;
58 }
