#include <bits/stdc++.h>

using namespace std;

const int maxn = 2600;

typedef double ld;

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

void dfs(int u) {
    siz[u] = 1;
    dp[u][1] = p[u] - 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]);
    }

    ld lower = 0;
    ld upper = 10005;
    while (upper - lower >= 1e-5) {
        mid = (lower + upper) / 2;  
        for (int i = 0; i <= n; i++) {
            for (int j = 0; j <= k+1; j++) {
                dp[i][j] = -1e16;
            }
        }
        dfs(0);
        if (dp[0][k+1] < 0) {
            upper = mid;
        } else {
            lower = mid;
        }
    }
    cout << fixed << setprecision(3);
    cout << (lower + upper) / 2 << endl;
}