#include <bits/stdc++.h>

using namespace std;

const int maxn = 2600;

typedef long long ll;

vector<int> g[maxn];
ll s[maxn], p[maxn];
int  r[maxn];
int siz[maxn];
ll dp[maxn][maxn];
ll mid;
int k;

void dfs(int u) {
    siz[u] = 1;
    dp[u][1] = p[u] * 10000 - mid * s[u];
    for (auto v : g[u]) {
        if (v != r[u]) {
            dfs(v);
            for (int i = min(k+1, siz[u] + siz[v]); i >= 2; i--) {
                for (int j = 1; j <= min(siz[v], i); j++) {
                    dp[u][i] = max(dp[u][i], dp[u][i-j] + dp[v][j]);
                }
            }
            siz[u] += siz[v];
        }
    }
}

int main() {
    int n;
    cin >> k >> n;
    for (int i = 1; i <= n; i++) {
        cin >> s[i] >> p[i] >> r[i];
        g[r[i]].push_back(i);
        g[i].push_back(r[i]);
    }

    ll lower = 0;
    ll upper = 100050000;
    ll ans = 0;
    while (lower <= upper) {
        mid = (lower + upper) / 2;  
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j <= k+1; j++) {
                dp[i][j] = -1ll << 50;
            }
        }
        dfs(0);
        if (dp[0][k+1] < 0) {
            upper = mid - 1;
        } else {
            lower = mid + 1;
            ans = mid;
        }
    }
    cout << fixed << setprecision(3);
    cout << double(ans / (double)10000 + 1e-5) << endl;
}