#include "bits/stdc++.h"

using namespace std;

using ll = long long;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
using vvvll = vector<vector<vector<ll>>>;
using vvvvll = vector<vector<vector<vector<ll>>>>;
using pl4 = pair<ll,ll>;
using str = string;
using vpl4 = vector<pair<ll,ll>>;

#define sz size()
#define be begin()
#define en end()
#define fi first
#define se second
#define pb push_back
#define mp make_pair

#define llin(x) ll (x);cin >>(x);
#define stin(x) str (x);cin >>(x);
#define vllin(x,n) vll (x)(n);FOR(i,0,n-1){cin >>(x)[i];}
#define vllin2(a,b,n) vll (a)(n);vll (b)(n);FOR(i,0,n-1){cin >>(a)[i]>>(b)[i];}
#define vllin3(a,b,c,n) vll (a)(n);vll (b)(n);vll (c)(n);FOR(i,0,n-1){cin >>(a)[i]>>(b)[i]>>(c)[i];}
#define vlling(x,n) (x).assign(n,0);FOR(i,0,n-1){cin >>(x)[i];}
#define vlling2(a,b,n) (a).assign(n,0);(b).assign(n,0);FOR(i,0,n-1){cin >>(a)[i]>>(b)[i];}
#define vlling3(a,b,c,n) (a).assign(n,0);(b).assign(n,0);(c).assign(n,0);FOR(i,0,n-1){cin >>(a)[i]>>(b)[i]>>(c)[i];}
#define vpl4in(x,n) vpl4 (x)((n),mp(0,0));FOR(i,0,n-1){cin >>x[i].fi>>x[i].se;}
#define FOR(i,a,b) for(ll i = a ; i <= b ; i++)
#define rFOR(i,b,a) for(ll i = a; i >= b ; i--)
#define SORT(x) sort(x.be, x.en)
#define rSORT(x) sort(x.rbegin(), x.rend())
#define say(x) cout<<(x);
#define sal(x) cout<<(x)<<endl;
#define says(x) cout<<(x)<<(' ');
#define sas cout<<(' ');
#define sayR(x) cout<<fixed<<setprecision(10)<<(x);
#define salR(x) cout<<fixed<<setprecision(10)<<(x)<<endl;
#define yn(a) cout <<((a)?"yes":"no")<<endl;
#define Yn(a) cout <<((a)?"Yes":"No")<<endl;
#define YN(a) cout <<((a)?"YES":"NO")<<endl;
#define Imp(a) cout <<((a)?"Possible":"Impossible")<<endl;
#define IMP(a) cout <<((a)?"POSSIBLE":"IMPOSSIBLE")<<endl;
#define pow(a,b) ll(pow(a,b))

ll MOD=1000000007;
ll INF=100000000000001;
vector<ll> value; // ノードの値を持つ配列
ll N;             // 葉の数
 
void update(ll i, ll x) {
    // i 番目の葉の値を x に変える
    i += N - 1; // i 番目の葉のノード番号
    value[i] = x;
    while (i > 0) {
        i = (i - 1) / 2; // ノード i の親ノードの番号に変える
        value[i] = min(value[i * 2 + 1],
                       value[i * 2 + 2]); // 左右の子の min を計算しなおす
    }
}
 
ll query(ll a, ll b, ll k, ll l, ll r) {
    // [a, b) の区間に対するクエリについて
    // ノード k （区間 [l, r) 担当）が答える
    if (r <= a || b <= l) return INF; // 区間が被らない場合は INF を返す
    if (a <= l && r <= b)
        return value[k]; // ノード k の担当範囲がクエリ区間 [a, b)
                         // に完全に含まれる
    else {
        ll c1 = query(a, b, 2 * k + 1, l, (l + r) / 2); // 左の子に値を聞く
        ll c2 = query(a, b, 2 * k + 2, (l + r) / 2, r); // 右の子に値を聞く
        return min(c1, c2); // 左右の子の値の min を取る
    }
}

ll n;
vll a(1000);
vll b(1000);
vll d(10001,100000000);
signed main(){
    llin(n);
    llin(d);
    d=d*2;
    llin(a);
    vpl4 x(n);
    ll h;
    FOR(i,0,n-1){
        cin >>x[i].fi>>h;
        x[i].se=(h-1)/a+1;
    }
    SORT(x);
    vll p(n);
    p[0]=x[0].se;
    ll s=x[0].se;
    ll c;
    ll ju;
    ll jd;
    FOR(i,1,n-1){
        if(x[i].fi<=x[0].fi+d){
            c=-1;
        }else{
        c=i/2;
        ju=i;
        jd=0;
        while(x[c+1].fi+d<x[i].fi || x[c].fi+d>=x[i].fi){
            if(x[c].fi+d>=x[i].fi){
                ju=c;
            }else{
                jd=c;
            }
            c=(jd+ju)/2;
        }
        }
        p[i]=(x[i].se-s+(c==-1?0:p[c])>0?x[i].se-s+(c==-1?0:p[c]):0);
        s+=p[i];
        p[i]=s;
    }
    sal(s)
}

Measured memory_bytes: 4992