#include<bits/stdc++.h>
#define ll long long
#define int long long
using namespace std;

const int maxn = 210000;

int wi[maxn];
vector<int>V[maxn];
int rt,n,W;
void input(int x)
{
	int k;
	cin>>wi[x]>>k;
	while(k--)
	{
		int y= ++n;
		V[x].emplace_back(y);
		input(y);
	}
}
int ans;
int dp(int x)
{
	ll sum=0;
	vector<int>Vc;
	for(auto y:V[x])
	{
		int yc=dp(y);
		if(yc!=0) sum+=yc,Vc.emplace_back(yc);
	}
	if(sum>W)
	{
		sort(Vc.begin(),Vc.end(),greater<int>());
		for(auto yc:Vc)
		{
			ans++;
			sum-=yc;
			if(sum<=W) break;
		}
	}
	if(sum==W) ans++,sum-=W;
	
	sum+=wi[x];
	ans+=sum/W;
	return sum%W;
}

signed main()
{
	ios_base::sync_with_stdio(false);
	
	cin>>W;
	rt=++n; input(rt);
	
	ans=0;
	int ww=dp(rt);
	if(ww!=0) ans++;
	cout<<ans<<endl;
	
	return 0;
}