#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;

const int MAX_N = 100010;

int n, s;
int a[MAX_N];
vector <int> v[MAX_N];

int df(int nod)
{
	int i, ret = 0;
	vector <int> b;
	
	for (i = 0; i < v[nod].size(); ++i)
	{
		int f = v[nod][i];
		
		ret += df(f);
		
		a[nod] += a[f];
		b.push_back(a[f]);
	}
	
	sort(b.begin(), b.end());
	
	for (; b.begin() != b.end() && a[nod] > s; b.pop_back())
	{
		a[nod] -= b[b.size() - 1];
		++ret;
	}
	
	return ret;
}

int main()
{
	int i, x, start;
	freopen("mese.in", "r", stdin);
	freopen("mese.out", "w", stdout);
	
	scanf("%d %d", &n, &s);
	
	for (i = 1; i <= n; ++i)
	{
		scanf("%d %d", &x, &a[i]);
		
		if (x) v[x].push_back(i);
		else start = i;
	}
	
	printf("%d\n", df(start) + 1);
}