#include <bits/stdc++.h>
#define ll long long
#define INF 1000000005
#define MOD 1000000007
#define EPS 1e-10
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define rrep(i,n) for(int i=(int)(n)-1;i>=0;--i)
#define srep(i,s,t) for(int i=(int)(s);i<(int)(t);++i)
#define each(a,b) for(auto& (a): (b))
#define all(v) (v).begin(),(v).end()
#define len(v) (int)(v).size()
#define zip(v) sort(all(v)),v.erase(unique(all(v)),v.end())
#define cmx(x,y) x=max(x,y)
#define cmn(x,y) x=min(x,y)
#define fi first
#define se second
#define pb push_back
#define show(x) cout<<#x<<" = "<<(x)<<endl
#define spair(p) cout<<#p<<": "<<p.fi<<" "<<p.se<<endl
#define sar(a,n) cout<<#a<<":";rep(pachico,n)cout<<" "<<a[pachico];cout<<endl
#define svec(v) cout<<#v<<":";rep(pachico,v.size())cout<<" "<<v[pachico];cout<<endl
#define svecp(v) cout<<#v<<":";each(pachico,v)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl
#define sset(s) cout<<#s<<":";each(pachico,s)cout<<" "<<pachico;cout<<endl
#define smap(m) cout<<#m<<":";each(pachico,m)cout<<" {"<<pachico.first<<":"<<pachico.second<<"}";cout<<endl

using namespace std;

typedef pair<int,int> P;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<double> vd;
typedef vector<P> vp;
typedef vector<string> vs;

const int MAX_N = 100005;

vi G[51];
vl v, w;
ll n, W, D;

void dfs(int u,int p)
{
    each(nx, G[u]){
        if(nx != p){
            dfs(nx,u);
            v[u] += v[nx];
            w[u] += w[nx];
        }
    }
}

//価値, 重さ
void dfs(ll value, ll weight, ll& opt, int index, vector<pll>& vec)
{
    if(index == n){
        cmx(opt, value);
        return;
    }
    //使う
    if(weight + vec[index].se <= W){
        cmx(opt, value + vec[index].fi);
        ll tweight = weight + vec[index].se;;
        ll tvalue = value + vec[index].fi;
        srep(i,index+1,n){
            if(tweight + vec[i].se <= W){
                tweight += vec[i].se;
                tvalue += vec[i].fi;
            }else{
                tvalue += vec[i].fi * (W - tweight) / vec[i].se;
                break;
            }
        }
        if(tvalue > opt){
            dfs(value+vec[index].fi,weight+vec[index].se,opt,index+1,vec);
        }
    }
    //使わない
    ll tweight = weight;
    ll tvalue = value;
    srep(i,index+1,n){
        if(tweight + vec[i].se <= W){
            tweight += vec[i].se;
            tvalue += vec[i].fi;
        }else{
            tvalue += vec[i].fi * (W - tweight) / vec[i].se;
            break;
        }
    }
    if(tvalue > opt){
        dfs(value,weight,opt,index+1,vec);
    }
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n >> W >> D;
    v.resize(n, 1), w.resize(n);
    cin >> w[0];
    rep(i,n-1){
        int p;
        cin >> w[i+1] >> p;
        G[p-1].pb(i+1);
    }
    dfs(0,-1);
    vector<pll> vec;
    rep(i,n){
        ll mx = W / w[i];
        if(i){
            cmn(mx, D);
        }
        ll cnt = 1;
        while(mx >= 2*cnt-1 && w[i]*cnt <= W){
            vec.pb(pll(v[i]*cnt, w[i]*cnt));
            cnt *= 2;
        }
        ll rem = mx-cnt+1;
        if(rem && w[i]*rem <= W){
            vec.pb(pll(v[i]*rem, w[i]*rem));
        }
    }
    sort(all(vec),[&](pll& a,pll& b){
        ll diff = a.fi * b.se - a.se * b.fi;
        return (diff != 0)?(diff>0):(a.fi>b.fi);
    });
    ll opt = 0;
    n = len(vec);
    dfs(0,0,opt,0,vec);
    cout << opt << "\n";
    return 0;
}


Measured memory_bytes: 512