#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;#define maxn 100005int head[maxn],cnt,E[maxn<<2],V[maxn<<2],du[maxn];int sta[maxn],top,n,m;double W[maxn<<2],dp[maxn][2],num[maxn];inline void in(int &now){    char Cget=getchar();now=0;    while(Cget>‘9‘||Cget<‘0‘) Cget=getchar();    while(Cget>=‘0‘&&Cget<=‘9‘)    {        now=now*10+Cget-‘0‘;        Cget=getchar();    }}inline void edge_add(int u,int v,double w){    E[++cnt]=head[u],V[cnt]=v,W[cnt]=w,head[u]=cnt;}int main(){    in(n),in(m);int u,v;double w;    for(;m--;)    {        in(u),in(v),du[v]++;        num[u]+=1.0;        scanf("%lf",&w);        edge_add(u,v,w);    }    dp[1][1]=1,sta[++top]=1;    while(top>0)    {        int now=sta[top--];        for(int i=head[now];i;i=E[i])        {            dp[V[i]][1]+=dp[now][1]/num[now],du[V[i]]--;            dp[V[i]][0]+=(dp[now][1]*W[i]+dp[now][0])/num[now];            if(!du[V[i]]) sta[++top]=V[i];        }    }    printf("%.2lf",dp[n][0]);    return 0;}