#include <bits/stdc++.h>
using namespace std;
#define int long long
//TEMPLATE START---------------8<---------------8<---------------8<---------------8<---------------//
typedef long long ll;       typedef long double ld;  typedef pair<int,int> pii; typedef pair<ll,ll> pll;  typedef vector<int> vi;   typedef vector<ll> vl;
typedef vector<string> vst; typedef vector<bool> vb; typedef vector<ld> vld;    typedef vector<pii> vpii; typedef vector<pll> vpll; typedef vector<vector<int> > vvi;
const int INF = (0x7FFFFFFFL); const ll INFF = (0x7FFFFFFFFFFFFFFFL); const string ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int MOD = 1e9 + 7;       const int MODD = 998244353;            const string alphabet = "abcdefghijklmnopqrstuvwxyz";
const double PI = acos(-1.0);  const double EPS = 1e-9;               const string Alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
int dx[9] = { 1, 0, -1,  0,  1, -1, -1, 1, 0 };
int dy[9] = { 0, 1,  0, -1, -1, -1,  1, 1, 0 };
#define ln '\n'
#define scnaf scanf
#define sacnf scanf
#define sancf scanf
#define SS(type, ...)type __VA_ARGS__;MACRO_VAR_Scan(__VA_ARGS__);
template<typename T> void MACRO_VAR_Scan(T& t){cin >> t;}template<typename First, typename...Rest> void MACRO_VAR_Scan(First& first, Rest&...rest){cin >> first;MACRO_VAR_Scan(rest...);}
#define SV(type,c,n) vector<type> c(n);for(auto& i:c)cin >> i;
#define SVV(type,c,n,m) vector<vector<type>> c(n,vector<type>(m));for(auto& r:c)for(auto& i:r)cin >> i;
template<class T,class U>ostream &operator<<(ostream &o,const pair<T,U>&j){o<<"{"<<j.first<<", "<<j.second<<"}";return o;}
template<class T,class U>ostream &operator<<(ostream &o,const map<T,U>&j){o<<"{";for(auto t=j.begin();t!=j.end();++t)o<<(t!=j.begin()?", ":"")<<*t;o<<"}";return o;}
template<class T>ostream &operator<<(ostream &o,const set<T>&j){o<<"{";for(auto t=j.begin();t!=j.end();++t)o<<(t!=j.begin()?", ":"")<<*t;o<<"}";return o;}
template<class T>ostream &operator<<(ostream &o,const multiset<T>&j){o<<"{";for(auto t=j.begin();t!=j.end();++t)o<<(t!=j.begin()?", ":"")<<*t;o<<"}";return o;}
template<class T>ostream &operator<<(ostream &o,const vector<T>&j){o<<"{";for(int i=0;i<(int)j.size();++i)o<<(i>0?", ":"")<<j[i];o<<"}";return o;}
inline int print(void){cout << endl; return 0;}
template<class Head> int print(Head&& head){cout << head;print();return 0;} template<class Head,class... Tail> int print(Head&& head,Tail&&... tail){cout<<head<<" ";print(forward<Tail>(tail)...);return 0;}
#ifdef LOCAL
inline int dump(void){cerr << endl; return 0;}
template<class Head> int dump(Head&& head){cerr << head;dump();return 0;}
template<class Head,class... Tail> int dump(Head&& head,Tail&&... tail){cerr<<head<<" ";dump(forward<Tail>(tail)...);return 0;}
#define debug(...) do{cerr<<__LINE__<<":	"<<#__VA_ARGS__<<" = ";dump(__VA_ARGS__);}while(0)
#define ER(x)  cerr << #x << " = " << (x) << endl;
#define ERV(v) {cerr << #v << " : ";for(const auto& xxx : v){cerr << xxx << " ";}cerr << "\n";}
#else
#define dump(...)
#define debug(...)
#define ER(x)
#define ERV(v)
#endif
template<typename T> void PA(T &a){int ASIZE=sizeof(a)/sizeof(a[0]);for(int ii=0;ii<ASIZE;++ii){cout<<a[ii]<<" \n"[ii==ASIZE-1];}}
template<typename T> void PV(T &v){int VSIZE=v.size();for(int ii=0;ii<VSIZE;++ii){cout<<v[ii]<<" \n"[ii==VSIZE-1];}}
inline int YES(bool x){cout<<((x)?"YES":"NO")<<endl;return 0;} inline int Yes(bool x){cout<<((x)?"Yes":"No")<<endl;return 0;}  inline int yes(bool x){cout<<((x)?"yes":"no")<<endl;return 0;}
inline int yES(bool x){cout<<((x)?"yES":"nO")<<endl;return 0;} inline int Yay(bool x){cout<<((x)?"Yay!":":(")<<endl;return 0;}
template<typename A,typename B> void sankou(bool x,A a,B b){cout<<((x)?(a):(b))<<endl;}
#define _overload3(_1,_2,_3,name,...) name
#define _REP(i,n) REPI(i,0,n)
#define REPI(i,a,b) for(ll i=ll(a);i<ll(b);++i)
#define REP(...) _overload3(__VA_ARGS__,REPI,_REP,)(__VA_ARGS__)
#define _RREP(i,n) RREPI(i,n,0)
#define RREPI(i,a,b) for(ll i=ll(a);i>=ll(b);--i)
#define RREP(...) _overload3(__VA_ARGS__,RREPI,_RREP,)(__VA_ARGS__)
#define EACH(e,v) for(auto& e : v)
#define PERM(v) sort((v).begin(),(v).end());for(bool c##p=1;c##p;c##p=next_permutation((v).begin(),(v).end()))
#define ADD(a,b) a=(a+ll(b))%MOD
#define MUL(a,b) a=(a*ll(b))%MOD
inline ll MOP(ll x,ll n,ll m=MOD){ll r=1;while(n>0){if(n&1)(r*=x)%=m;(x*=x)%=m;n>>=1;}return r;}
inline ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}inline ll lcm(ll a,ll b){return a*b/gcd(a,b);}inline ll POW(ll a,ll b){ll c=1ll;do{if(b&1)c*=1ll*a;a*=1ll*a;}while(b>>=1);return c;}
template<typename T,typename A,typename B> inline bool between(T x,A a,B b) {return ((a<=x)&&(x<b));}template<class T> inline T sqr(T x){return x*x;}
template<typename A,typename B> inline bool chmax(A &a,const B &b){if(a<b){a=b;return 1;}return 0;}
template<typename A,typename B> inline bool chmin(A &a,const B &b){if(a>b){a=b;return 1;}return 0;}
#define tmax(x,y,z) max((x),max((y),(z)))
#define tmin(x,y,z) min((x),min((y),(z)))
#define PB emplace_back
#define MP make_pair
#define MT make_tuple
#define all(v) (v).begin(),(v).end()
#define rall(v) (v).rbegin(),(v).rend()
#define SORT(v) sort((v).begin(),(v).end())
#define RSORT(v) sort((v).rbegin(),(v).rend())
#define EXIST(s,e) (find((s).begin(),(s).end(),(e))!=(s).end())
#define EXISTST(s,c) (((s).find(c))!=string::npos)
#define POSL(x,val) (lower_bound(x.begin(),x.end(),val)-x.begin())
#define POSU(x,val) (upper_bound(x.begin(),x.end(),val)-x.begin())
#define GEQ(x,val) (int)(x).size() - POSL((x),(val))
#define GREATER(x,val) (int)(x).size() - POSU((x),(val))
#define LEQ(x,val) POSU((x),(val))
#define LESS(x,val) POSL((x),(val))
#define SZV(a) int((a).size())
#define SZA(a) sizeof(a)/sizeof(a[0])
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
#define MEMINF(a) memset(a,0x3f,sizeof(a))
#define FILL(a,b) memset(a,b,sizeof(a))
#define UNIQUE(v) sort((v).begin(),(v).end());(v).erase(unique((v).begin(),(v).end()),(v).end())
struct abracadabra{
    abracadabra(){
        cin.tie(0); ios::sync_with_stdio(0);
        cout << fixed << setprecision(20);
        cerr << fixed << setprecision(5);
    };
} ABRACADABRA;

//TEMPLATE END---------------8<---------------8<---------------8<---------------8<---------------//

template <typename Monoid, typename OperatorMonoid = Monoid> struct LazySegmentTree {
    typedef function< Monoid(Monoid, Monoid) > F;
    typedef function< Monoid(Monoid, OperatorMonoid) > G;
    typedef function< OperatorMonoid(OperatorMonoid, OperatorMonoid) > H;
    typedef function< OperatorMonoid(OperatorMonoid, int) > P;
    int sz;
    F f; G g; H h; P p;
    Monoid d1; OperatorMonoid d0;
    vector< Monoid > dat;
    vector< OperatorMonoid > laz;
    LazySegmentTree(int n, F f, G g, H h, Monoid d1, OperatorMonoid d0,
        vector< Monoid > v = vector< Monoid >(), P p = [] (OperatorMonoid a, int b) { return a; })
        : f(f), g(g), h(h), d1(d1), d0(d0), p(p) {
        sz = 1; while (sz < n) sz <<= 1;
        dat.assign(2 * sz - 1, d1);
        laz.assign(2 * sz - 1, d0);
        if (n == (int)v.size()) build(n, v);
    }
    void build(int n, vector<Monoid> &v) {
        for (int i = 0; i < n; ++i) dat[i + sz - 1] = v[i];
        for (int i = sz - 2; i >= 0; --i) dat[i] = f(dat[2 * i + 1], dat[2 * i + 2]);
    }
    inline void eval(int len, int k) {
        if (laz[k] == d0) return;
        if (2 * k + 1 < 2 * sz - 1) {
            laz[2 * k + 1] = h(laz[2 * k + 1], laz[k]);
            laz[2 * k + 2] = h(laz[2 * k + 2], laz[k]);
        }
        dat[k] = g(dat[k], p(laz[k], len));
        laz[k] = d0;
    }
    Monoid update(int a, int b, OperatorMonoid x, int k, int l, int r) {
        eval(r - l, k);
        if (r <= a or b <= l) return dat[k];
        if (a <= l and r <= b) {
            laz[k] = h(laz[k], x);
            return g(dat[k], p(laz[k], r - l));
        }
        return dat[k] = f(update(a, b, x, 2 * k + 1, l, (l + r) / 2), update(a, b, x, 2 * k + 2, (l + r) / 2, r));
    }
    Monoid update(int a, int b, OperatorMonoid x) {
        return update(a, b, x, 0, 0, sz);
    }
    Monoid query(int a, int b, int k, int l, int r) {
        eval(r - l, k);
        if (r <= a or b <= l) return d1;
        if (a <= l and r <= b) return dat[k];
        Monoid vl = query(a, b, 2 * k + 1, l, (l + r) / 2);
        Monoid vr = query(a, b, 2 * k + 2, (l + r) / 2, r);
        return f(vl, vr);
    }
    Monoid query(int a, int b) {
        return query(a, b, 0, 0, sz);
    }
    Monoid operator[](const int &k) {
        return query(k, k + 1);
    }
};

/*
・遅延評価セグメント木
    > query, update O(logN)
[引数]
LazySegmentTree<Monoid, OperatorMonoid> seg(sz, f, g, h, d1, d0, v, p);
> sz : 要素数
>  f : 要素と要素をマージする関数
>  g : 要素に作用素を作用させる関数
>  h : 作用素と作用素をマージする関数
> d1 : 要素のモノイド
> d0 : 作用素のモノイド
>  v : 初期化用の配列
>  p : 区間に対する操作が要素数に比例して変化する場合 ( p(a, b) = g(a, a, ..., a) [aはb個] )
[備考]
以下の3つの条件を満たすときに使える
1. g(f(a, b), c) = f(g(a, c), g(b, c))
( 1'. g(f(a, b), p(c, d)) = f(g(a, p(c, d / 2)), g(b, p(c, d / 2))) )
2. g(g(a, b), c) = g(a, h(b, c))
3. g(a, d0) = a
[典型例]
> 区間加算 -> 区間和
LazySegmentTree<ll> seg(N, plus<ll>(), plus<ll>(), plus<ll>(), 0, 0, vector<ll>(N, 0), multiplies<ll>());
> 区間加算 -> 区間最小
LazySegmentTree<ll> seg(N, [](ll a, ll b){ return min(a, b); }, plus<ll>(), plus<ll>(), INFF, 0);
> 区間更新 -> 区間和
LazySegmentTree<ll> seg(N, plus<ll>(), [](ll a, ll b){ return b; }, [](ll a, ll b){ return b; }, 0, INFF, vector<ll>(N, 0), multiplies<ll>());
> 区間更新 -> 区間最小
LazySegmentTree<ll> seg(N, [](ll a,ll b){ return min(a,b); }, [](ll a, ll b){ return b; }, [](ll a, ll b){ return b; }, INFF, INFF);
[使用例]
seg.update(l, r, x);        // 半開区間[l, r)に作用素xを作用
seg.query(l, r);            // 半開区間[l, r)に対する演算の結果
seg[k];                     // k番目の要素を取得
*/

signed main() {

    SS(int, N, D, A);

    
    vpii xh;
    REP(i, N) {
        SS(int, X, H);
        xh.PB(X, H);
    }
    SORT(xh);

    vector<ll> v;
    EACH(e, xh) v.emplace_back(e.second);
    LazySegmentTree<ll> seg(N, plus<ll>(), plus<ll>(), plus<ll>(), 0, 0, v, multiplies<ll>());

    auto get = [&](int x) -> int {
        int y = x + 2 * D + 1;
        return POSL(xh, MP(y, -INF));
    };

    ll res = 0;
    REP(i, N) {
        if (seg[i] <= 0) continue;
        int x = xh[i].first;
        int y = (seg[i] + A - 1) / A;
        res += y;
        seg.update(i, get(x), -y * A);
    }
    print(res);

}

Measured memory_bytes: 15724