#include <bits/stdc++.h>
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define rep(i,N) for(long long i = 0; i < (long long)(N); i++)
#define repr(i,N) for(long long i = (long long)(N) - 1; i >= 0; i--)
#define rep1(i,N) for(long long i = 1; i <= (long long)(N) ; i++)
#define repr1(i,N) for(long long i = (N) ; (long long)(i) > 0 ; i--)
#define each(x,v) for(auto& x : v)
#define all(v) (v).begin(),(v).end()
#define sz(v) ((int)(v).size())
#define ini(...) int __VA_ARGS__; in(__VA_ARGS__)
#define inl(...) long long __VA_ARGS__; in(__VA_ARGS__)
#define ins(...) string __VA_ARGS__; in(__VA_ARGS__)
#define in2(N,s,t) rep(i,N){in(s[i] , t[i]);}
#define in3(N,s,t,u) rep(i,N){in(s[i] , t[i] , u[i]);}
using namespace std; void solve();
using ll = long long; template<class T = ll> using V = vector<T>;
using vi = V<int>; using vl = V<>; using vs = V<string>;
using vd = V<double>; using vvi = V< V<int> >; using vvl = V< V<> >;
template<typename T>using heap = priority_queue< T , V<T> , greater<T> >;
constexpr int inf = 1001001001; constexpr ll infLL = (1LL << 61) - 1;
struct IoSetupNya {IoSetupNya() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); cerr << fixed << setprecision(7);} } iosetupnya;
template<typename T, typename U> inline bool amin(T &x, U y) { return (y < x) ? (x = y, true) : false; }
template<typename T, typename U> inline bool amax(T &x, U y) { return (x < y) ? (x = y, true) : false; }
template<typename T, typename U> ostream& operator <<(ostream& os, const pair<T, U> &p) { os << p.first << " " << p.second; return os; }
template<typename T, typename U> istream& operator >>(istream& is, pair<T, U> &p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator <<(ostream& os, const vector<T> &v) { int s = (int)v.size(); rep(i,s) os << (i ? " " : "") << v[i]; return os; }
template<typename T> istream& operator >>(istream& is, vector<T> &v) { for(auto &x : v) is >> x; return is; }
void in(){} template <typename T,class... U> void in(T &t,U &...u){ cin >> t; in(u...);}
void out(){cout << "\n";} template <typename T,class... U> void out(const T &t,const U &...u){ cout << t; if(sizeof...(u)) cout << " "; out(u...);}
template<typename T>void die(T x){out(x); exit(0);}
#ifdef NyaanDebug
  #include "NyaanDebug.h"
  #define trc(...) do { cerr << #__VA_ARGS__ << " = "; dbg_out(__VA_ARGS__);} while(0)
  #define trca(v,N) do { cerr << #v << " = "; array_out(v , N);cout << endl;} while(0)
#else
  #define trc(...)
  #define trca(...)
  int main(){solve();}
#endif

using P = pair<ll,ll>; using vp = V<P>;
constexpr int MOD = /**/ 1000000007; //*/ 998244353;
//////////////////

// 遅延伝播セグメント木
template <typename T,typename E,typename F,typename G,typename H>
struct LST{
  int n,height;
  F f;
  G g;
  H h;
  T ti;
  E ei;
  vector<T> dat;
  vector<E> laz;
  LST(int n, F f,G g,H h,T ti,E ei):
    f(f),g(g),h(h),ti(ti),ei(ei){
      init(n);
  }
  LST(const vector<T> &v, F f,G g,H h,T ti,E ei):
    f(f),g(g),h(h),ti(ti),ei(ei){
      init( (int)v.size() );
      build(v);
  }
  
  void init(int n_){
    n=1;height=0;
    while(n<n_) n<<=1,height++;
    dat.assign(2*n,ti);
    laz.assign(2*n,ei);
  }
  void build(const vector<T> &v){
    int n_=v.size();
    init(n_);
    for(int i=0;i<n_;i++) dat[n+i]=v[i];
    for(int i=n-1;i;i--)
      dat[i]=f(dat[(i<<1)|0],dat[(i<<1)|1]);
  }
  inline T reflect(int k){
    return laz[k]==ei?dat[k]:g(dat[k],laz[k]);
  }
  inline void eval(int k){
    if(laz[k]==ei) return;
    laz[(k<<1)|0]=h(laz[(k<<1)|0],laz[k]);
    laz[(k<<1)|1]=h(laz[(k<<1)|1],laz[k]);
    dat[k]=reflect(k);
    laz[k]=ei;
  }
  inline void thrust(int k){
    for(int i=height;i;i--) eval(k>>i);
  }
  inline void recalc(int k){    
    while(k>>=1)
      dat[k]=f(reflect((k<<1)|0),reflect((k<<1)|1));
  }
  void update(int a,int b,E x){
    thrust(a+=n);
    thrust(b+=n-1);
    for(int l=a,r=b+1;l<r;l>>=1,r>>=1){
      if(l&1) laz[l]=h(laz[l],x),l++;
      if(r&1) --r,laz[r]=h(laz[r],x);
    }
    recalc(a);
    recalc(b);
  }
  void set_val(int a,T x){
    thrust(a+=n);
    dat[a]=x;laz[a]=ei;
    recalc(a);
  }
  T query(int a,int b){
    thrust(a+=n);
    thrust(b+=n-1);
    T vl=ti,vr=ti;
    for(int l=a,r=b+1;l<r;l>>=1,r>>=1) {
      if(l&1) vl=f(vl,reflect(l++));
      if(r&1) vr=f(reflect(--r),vr);
    }
    return f(vl,vr);
  }
};


void solve(){
  inl(N,D,A);
  vp p(N); in(p);
  sort(all(p));

  // 区間にaを足す・区間最大
  using T = pair<ll, ll>;
  using E = ll;
  constexpr T T_UNIT = T(-infLL, 0);
  constexpr E E_UNIT = 0;
  auto f = [](T a, T b){
    return T( max(a.fi, b.fi) , a.se + b.se);
  };
  auto gg = [](T a, E b){
    return T(a.fi + b, a.se);
  };
  auto h = [](E a, E b){
    return a + b;
  };

  vl x(N); rep(i,N) x[i] = p[i].fi;

  vector<T> v(N , T(0,1));
  rep(i , N) v[i].fi = p[i].se;

  LST<T, E, decltype(f), decltype(gg), decltype(h)>
    seg(v,f,gg,h,T_UNIT,E_UNIT);

  ll ans = 0;
  while(1){
    if(seg.query(0 , N).fi <= 0) break;
    // 最も左の生きてるモンスター
    int ok = 0 , ng = N;
    while(ok + 1 < ng){
      int med = (ok + ng) / 2;
      if(seg.query(0 , med).fi > 0) ng = med;
      else ok = med;
    }
    // okが左の生きているモンスター

    ll hp = seg.query(ok , ok + 1).fi;
    trc(ok , hp);
    ll times = ( hp + A - 1 ) / A;
    ans += times;

    ll left = p[ok].fi;
    auto li = lower_bound(all(x) , left);
    ll right = p[ok].fi + 2 * D;
    auto ri = upper_bound(all(x) , right);
    trc(left , right);
    trc(li - begin(x) , ri - begin(x));

    seg.update(li - begin(x) , ri - begin(x) , -times * A);
  }

  out(ans);


}

Measured memory_bytes: 20352