#include <map>

#include <cmath>

#include <queue>

#include <cstdio>

#include <cstring>

#include <iostream>

#include <algorithm>

using namespace std;

#define F(i,j,k) for (int i=j;i<=k;++i)

#define D(i,j,k) for (int i=j;i>=k;--i)

#define ll long long

#define inf 1e15

#define eps 1e-6

#define mp make_pair

#define maxn 2505

int k,n;

double s[maxn],p[maxn],l,r,mid,dp[maxn][maxn],tmp[maxn];

int h[maxn],to[maxn],ne[maxn],en=0,siz[maxn];

void add(int a,int b)

{to[en]=b;ne[en]=h[a];h[a]=en++;}

void Tree_DP(int o)

{

    dp[o][1]=p[o]-mid*s[o];siz[o]=1;

    for (int i=h[o];i>=0;i=ne[i])

    {

        Tree_DP(to[i]);

        F(j,0,siz[o]+siz[to[i]]) tmp[j]=-inf;

        F(j,1,siz[o]) F(k,0,siz[to[i]])

            tmp[j+k]=max(tmp[j+k],dp[o][j]+dp[to[i]][k]);

        F(j,0,siz[o]+siz[to[i]]) dp[o][j]=max(dp[o][j],tmp[j]);

        siz[o]+=siz[to[i]];

    }

}

int main()

{

    memset(h,-1,sizeof h);

    scanf("%d%d",&k,&n);k++;

    F(i,1,n)

    {

        int x;

        scanf("%lf%lf%d",&s[i],&p[i],&x);

        add(x,i);

    }

    l=0;r=1e10;

    while (fabs(r-l)>eps)

    {

        mid=(l+r)/2;

        F(i,0,n) F(j,0,k) dp[i][j]=-inf;

        s[0]=1;p[0]=mid;

        Tree_DP(0);

        int flag=0;

        if (dp[0][k]>=0) l=mid;

        else r=mid;

    }

    printf("%.3f\n",l);

}