#include <bits/stdc++.h>
using namespace std;

const int maxn = 3000,inf = 1e9+7;

int n,k;

struct node{
	int to,nxt;
}ed[maxn];

int head[maxn],tot;

void add(int u,int to){
	ed[++tot].to = to;
	ed[tot].nxt = head[u];
	head[u] = tot;
}

int siz[maxn],dfn[maxn],pos[maxn],cnt;

void dfs(int x){
	siz[x] = 1;
	for (int i = head[x];i;i = ed[i].nxt){
		int to = ed[i].to;
		dfs(to);
		siz[x] += siz[to];
	}
	dfn[x] = ++cnt,pos[cnt] = x;
}

double val[maxn],f[maxn][maxn];
int p[maxn],s[maxn];

bool check(double x){
	for (int i = 0;i <= cnt;i++)
		for (int j = 1;j <= k;j++)
			f[i][j]=-inf;
	for (int i = 1;i <= n;i++)
		val[i] = (double)p[i]-x*s[i];
	for (int i = 1;i <= cnt;i++){
		for (int j = 1;j <= k;j++){
			f[i][j] = max(f[i-1][j-1]+val[pos[i]],f[i-siz[pos[i]]][j]);
		}
	}
	return f[cnt][k]>0;
}

int main(){
	freopen("bestteam.in","r",stdin);
	freopen("bestteam.out","w",stdout); 
	scanf("%d%d",&k,&n);
	k++;
	for (int i = 1;i <= n;i++){
		int x;
		scanf("%d%d%d",&s[i],&p[i],&x); 
		add(x,i);
	} 
	dfs(0);
	double l = 0,r = 100000,eps = 1e-4;
	while (r-l >= eps){
		double mid=(l+r)/2;
		if (check(mid)) l=mid;
		else r=mid;
	}
	printf("%.3lf\n",l);
	return 0;
}