#include <fstream>
#include <vector>
#include <bitset>
#include <queue>
#include <algorithm>
#include <utility>
#include <cstring>
#include <string>
#include <stack>
#include <deque>
#include <iomanip>
#include <set>
#include <map>
#include <cassert>
#include <ctime>

using namespace std;

ifstream cin("mese.in");
ofstream cout("mese.out");

const int MAXN = 100001;
const int oo = (1<<31)-1;

typedef vector<int> Graph[MAXN];
typedef vector<int> :: iterator It;

const inline int min(const int &a, const int &b) { if( a > b ) return b;   return a; }
const inline int max(const int &a, const int &b) { if( a < b ) return b;   return a; }
const inline void Get_min(int &a, const int b)    { if( a > b ) a = b; }
const inline void Get_max(int &a, const int b)    { if( a < b ) a = b; }

Graph G;
int N, S, Age[MAXN], Ans;

struct ClassComp {
    inline bool operator () (const int &a, const int &b) const {
        return Age[a] < Age[b];
    }
};

inline void DFs(int Node) {
    for (It it = G[Node].begin(), fin = G[Node].end(); it != fin ; ++ it)
        DFs(*it),
        Age[Node] += Age[*it];
    stable_sort(G[Node].begin(), G[Node].end(), ClassComp());
    for(vector<int> :: reverse_iterator it = G[Node].rbegin() ; Age[Node] > S && it != G[Node].rend() ; ) {
        Age[Node] -= Age[*it];
        ++ Ans;
        ++ it;
    }
}

int main() {
    cin >> N >> S;
    for(int i = 1 ; i <= N ; ++ i) {
        int x, y;
        cin >> x >> Age[i];
        G[x].push_back(i);
    }
    DFs(0);
    cout << ++ Ans << '\n';
    cin.close();
    cout.close();
    return 0;
}