#include<iostream>

#include<cstdio>

#include<cstring>

#include<string>

#include<algorithm>

#include<cctype>

#include<cmath>

#include<cstdlib>

#include<queue>

#include<ctime>

#include<vector>

#include<set>

#include<map>

#include<stack>

using namespace std;

int n,m;

int s[],p[],r[],siz[];

double dp[][];

vector<int>v[];

inline void go(int x,double mid){

    dp[x][]=double(p[x]-s[x]*mid);

    siz[x]=;

    for(int i=;i<v[x].size();i++){

      go(v[x][i],mid);

      for(int j=siz[x];j>;j--)

        for(int k=;k<=siz[v[x][i]];k++)

          dp[x][j+k]=max(dp[x][j+k],dp[x][j]+dp[v[x][i]][k]);

      siz[x]+=siz[v[x][i]];

    }

}

inline bool ck(double mid){

    memset(dp,-,sizeof(dp));

    s[]=p[]=;

    go(,mid);

    return dp[][m+]>=;

}

signed main(){

    int i,j,k;

    scanf("%d%d",&m,&n);

    for(i=;i<=n;i++){

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

      v[r[i]].push_back(i);

    }

    double le=,ri=10000.0001;

    while(ri-le>0.0001){

      double mid=(le+ri)/;

      if(ck(mid))le=mid;

        else ri=mid;

    }

    printf("%0.3lf\n",le);

    return ;

}