#include <algorithm>
#include <fstream>
#include <vector>

using namespace std;

ifstream fin("mese.in");
ofstream fout("mese.out");

const int nmax= 100000;

int ans;
int sum[nmax+1], v[nmax+1];

vector <int> g[nmax+1];

void dfs( int x, int s ) {
    for ( vector <int>::iterator it= g[x].begin(); it!=g[x].end(); ++it ) {
        dfs(*it, s);
    }

    for ( int i= 0; i<(int)g[x].size(); ++i ) {
        v[i]= sum[g[x][i]];
    }
    sort( v, v+(int)g[x].size() );
    for ( int i= 0; i<(int)g[x].size() && v[i]+sum[x]<=s; ++i, ++ans ) {
        sum[x]+= v[i];
    }
}

int main(  ) {
    int n, s;
    fin>>n>>s;
    for ( int i= 1, f; i<=n; ++i ) {
        fin>>f>>sum[i];
        g[f].push_back(i);
    }

    dfs(0, s);

    fout<<n+1-ans<<"\n";

    return 0;
}