#include <iostream>
#include <cstring>
#include <map>
#include <cstdio>
#include <queue>
#include <algorithm>
#define ll long long
using namespace std;

struct node
{
	int x;
	int nxt;
};

const int maxn = 100000 + 5;

int Max_w;
node a[maxn << 1];
int len, h[maxn];
int w[maxn];
int chuan[maxn];
int tot;
int ans;

template<class T>
inline void read(T &x);

inline void add(int x, int y)
{
	len++; a[len].x = y; a[len].nxt = h[x]; h[x] = len;
}

void input(int x, int fa)
{
	add(x, fa); add(fa, x);
	int n;
	read(w[x]); read(n);
	
	for (int i = 1; i <= n; i++)
		input(++tot,x);
}

void init()
{
    read(Max_w);
    input(++tot,0);
}

priority_queue<int > q[maxn];

void dfs(int x, int fa)
{
	// printf("x:%d fa:%d w:%d\n",x,fa,w[x]);
	ll tot_chuan = 0;
	
	for (int p = h[x]; p; p = a[p].nxt)
	{
		int v = a[p].x;
		if (v == fa) continue;
		dfs(v,x);
		
		if (chuan[v]) q[x].push(chuan[v]), tot_chuan += chuan[v];
	}

	while (tot_chuan > Max_w)
	{
		int t = q[x].top();
		q[x].pop();
		tot_chuan -= t;
		ans++;
	}
	
	w[x] += tot_chuan;

	ans += w[x]/Max_w;
	w[x] %= Max_w;

	chuan[x] = w[x];
}

void work()
{
    dfs(1,0);
	if (chuan[1] != 0) ans++;
	// for (int i = 1; i <= tot; i++) cout << chuan[i] << ' ';
	// puts("");
}

void print()
{
    cout << ans << endl;
}

int main()
{
//    freopen("test.in","r",stdin);
//    freopen("test.out","w",stdout);

    init();
    work();
    print();

    return 0;
}

template<class T>
inline void read(T &x)
{
    x = 0; T s = 1;
    char c = getchar();
    while(c < '0' || c > '9') {if(c == '-') s = -1; c = getchar();}
    while(c >= '0' && c <= '9') {x = x*10+c-'0'; c = getchar();}
    x *= s;
}