#include <iostream>#include <cstring>#include <cstdlib>#include <cstdio>#include <algorithm>#include <cmath>#define N 1100#define M 1000100using namespace std;int a[M],b[M];int head[N],next[M],to[M];int q[M*5],im[N];int vis[N];int n,cnt,m,st;double l,r,mid,c[M],dis[N],len[M],val[N];inline void add(int u,int v,double w){ to[cnt]=v; len[cnt]=w; next[cnt]=head[u]; head[u]=cnt++;}inline void read(){ memset(head,-1,sizeof head); cnt=0; for(int i=1;i<=n;i++) scanf("%lf",&val[i]); for(int i=1;i<=m;i++) { scanf("%d%d%lf",&a[i],&b[i],&c[i]); add(a[i],b[i],c[i]); }}inline bool dfs(int u){ vis[u]=st; for(int i=head[u];~i;i=next[i]) if(dis[to[i]]>dis[u]+len[i]*mid-val[u]) { dis[to[i]]=dis[u]+len[i]*mid-val[u]; if(vis[to[i]]==st) return true; else if(dfs(to[i])) return true; } vis[u]=0; return false;}//dfs-spfa找负环 inline bool spfa(){ memset(vis,0,sizeof vis); for(st=1;st<=n;st++) if(dfs(st)) return true; return false;}inline void go(){ l=0.0; r=1000.0; while(r-l>1e-4) { mid=(l+r)/2.0; if(spfa()) l=mid; else r=mid; } printf("%.2lfn",mid);}int main(){ while(scanf("%d%d",&n,&m)!=EOF) read(),go(); return 0;}
