/**
 *	author: nok0
 *	created: 2020.09.08 19:55:29
**/
#include<bits/stdc++.h>
using namespace std;
#pragma region Macros
#define ll long long
#define ld long double
#define FOR(i,l,r) for(int i=(l);i<(r);++i)
#define REP(i,n) FOR(i,0,n)
#define REPS(i,n) FOR(i,1,n+1)
#define RFOR(i,l,r) for(int i=(l);i>=(r);--i)
#define RREP(i,n) RFOR(i,n-1,0)
#define RREPS(i,n) RFOR(i,n,1)
#define pb push_back
#define eb emplace_back
#define SZ(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
template<class T = int> using V = vector<T>;
template<class T = int> using VV = V<V<T>>;
using P = pair<ll, ll>;
#define VEC(type, name, size)\
	V<type> name(size);\
	IN(name)
#define VVEC(type, name, h, w)\
	VV<type> name(h, V<type>(w));\
	IN(name)
#define INT(...)\
	int __VA_ARGS__;\
	IN(__VA_ARGS__)
#define LL(...)\
	ll __VA_ARGS__;\
	IN(__VA_ARGS__)
#define STR(...)\
	string __VA_ARGS__;\
	IN(__VA_ARGS__)
#define CHAR(...)\
	char __VA_ARGS__;\
	IN(__VA_ARGS__)
#define DOUBLE(...)\
	DOUBLE __VA_ARGS__;\
	IN(__VA_ARGS__)
#define LD(...)\
	LD __VA_ARGS__;\
	IN(__VA_ARGS__)
template <class T> void scan(T a) { cin >> a; }
void scan(int &a) { cin >> a; }
void scan(long long &a) { cin >> a; }
void scan(char &a) { cin >> a; }
void scan(double &a) { cin >> a; }
void scan(long double &a) { cin >> a; }
void scan(char a[]) { scanf("%s", a); }
void scan(string &a) { cin >> a; }
template <class T> void scan(V<T> &);
template <class T, class L> void scan(pair<T, L> &);
template <class T> void scan(V<T> &a) { for(auto &i : a) scan(i); }
template <class T, class L> void scan(pair<T, L> &p){ scan(p.first); scan(p.second); }
template <class T> void scan(T &a) { cin >> a; }
void IN() {}
template <class Head, class... Tail> void IN(Head &head, Tail &... tail) { scan(head); IN(tail...); }
template <class T> inline void print(T x){ cout << x << '\n';}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p){
	is >> p.first >> p.second;
	return is;
}
template <typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p){
	os << p.first << " " << p.second;
	return os;
}
template <class T>
ostream &operator<<(ostream &os, const V<T> &v){
	REP(i, SZ(v)){
		if(i) os << " ";
		os << v[i];
	}
	return os;
}
//debug
template <typename T>
void view(const V<T> &v){
	cerr << "{ ";
	for(const auto &e : v){
		cerr << e << ", ";
	}
	cerr << "\b\b }";
}
template <typename T>
void view(const VV<T> &vv){
	cerr << "{\n";
	for(const auto &v : vv){
		cerr << "\t";
		view(v);
		cerr << "\n";
	}
	cerr << "}";
}
template <typename T, typename U>
void view(const V<pair<T, U>> &v){
	cerr << "{\n";
	for(const auto &c : v) cerr << "\t(" << c.first << ", " << c.second << ")\n";
	cerr << "}";
}
template <typename T, typename U>
void view(const map<T, U> &m){
	cerr << "{\n";
	for(auto &t : m) cerr << "\t[" << t.first << "] : " << t.second << "\n";
	cerr << "}";
}
template <typename T, typename U>
void view(const pair<T, U> &p){ cerr << "(" << p.first << ", " << p.second << ")";}
template <typename T>
void view(const set<T> &s) {
	cerr << "{ ";
	for(auto &t : s) {
		view(t);
		cerr << ", ";
	}
	cerr << "\b\b }";
}
template <typename T>
void view(T e) { cerr << e;}
#ifdef LOCAL
void debug_out() {}
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
	view(H);
	cerr << ", ";
	debug_out(T...);
}
#define debug(...)                                           \
	do{                                                     \
		cerr << __LINE__ << " [" << #__VA_ARGS__ << "] : ["; \
		debug_out(__VA_ARGS__);                              \
		cerr << "\b\b]\n";                                   \
	} while(0)
#else
#define debug(...) (void(0))
#endif
template <class T> V<T> press(V<T> &x){ 
	V<T> res = x;
	sort(all(res));
	res.erase(unique(all(res)), res.end());
	REP(i, SZ(x)){
		x[i] = lower_bound(all(res), x[i]) - res.begin();
	}
	return res;
}
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return true; }return false; }
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return true; }return false; }
inline void Yes(bool b = true) {cout << (b ? "Yes" : "No") << '\n';}
inline void YES(bool b = true) {cout << (b ? "YES" : "NO") << '\n';}
inline void err(bool b = true) {if(b) {cout << -1 << '\n'; exit(0);}}
template<class T> inline void fin(bool b = true, T e = 0) {if(b) {cout << e << '\n'; exit(0);}}
template<class T> T divup(T x, T y) {return (x+(y-1))/y;}
template <typename T> T pow(T a, long long n, T e = 1) {T ret = e; while (n) {if (n & 1) ret *= a; a *= a; n >>= 1; } return ret; }
struct iofast{iofast(){ios::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(15);}}iofast_;
const int inf = 1e9;
const ll INF = 1e18;
#pragma endregion

template <class Monoid, class E>
struct LazySegmentTree{
private:
	using F = function<Monoid(Monoid, Monoid)>;
	using G = function<Monoid(Monoid, E)>;
	using H = function<E(E, E)>;
	int n, height;
	V<Monoid> Node;
	V<E> Lazy;
	F f;
	G g;
	H h;
	Monoid Monoid_unit, init_data;
	E e_unit;

	void build(V<Monoid> vec){
		Node.assign(2 * n, init_data);
		REP(i, n) Node[i + n] = vec[i];
		RREP(i, n) Node[i] = f(Node[i << 1], Node[i << 1 | 1]);
		Lazy.assign(2 * n, e_unit);
		height = 0;
		for(int i = 1; i <= n; i *= 2) height++;
	}

	void eval(int left, int right){
		left += n, right += n - 1;
		RREPS(i, height){
			int l = left >> i, r = right >> i;
			Lazy[l << 1] = h(Lazy[l << 1], Lazy[l]);
			Lazy[l << 1 | 1] = h(Lazy[l << 1 | 1], Lazy[l]);
			Node[l] = g(Node[l], Lazy[l]);
			Lazy[l] = e_unit;
			Lazy[r << 1] = h(Lazy[r << 1], Lazy[r]);
			Lazy[r << 1 | 1] = h(Lazy[r << 1 | 1], Lazy[r]);
			Node[r] = g(Node[r], Lazy[r]);
			Lazy[r] = e_unit;
		}
	}

public:
	LazySegmentTree(V<Monoid> vec, F f_, G g_, H h_, Monoid Monoid_unit_, E e_unit_)
	:n(SZ(vec)), f(f_), g(g_), h(h_), Monoid_unit(Monoid_unit_), e_unit(e_unit_){
		build(vec);
	}

	LazySegmentTree(int n_, F f_, G g_, H h_, Monoid Monoid_unit_, E e_unit_)
	:n(n_), f(f_), g(g_), h(h_), Monoid_unit(Monoid_unit_), e_unit(e_unit_), init_data(Monoid_unit_){
		build(V<Monoid>(n, init_data));
	}

	LazySegmentTree(int n_, F f_, G g_, H h_, Monoid Monoid_unit_, E e_unit_, Monoid init_data_)
	:n(n_), f(f_), g(g_), h(h_), Monoid_unit(Monoid_unit_), e_unit(e_unit_), init_data(init_data_){
		build(V<Monoid>(n, init_data));
	}

	void update(int left, int right, E operator_){
		eval(left, right);
		left += n, right += n;
		int L0 = left / (left & -left);
		int R0 = right / (right & -right);
		while(left < right) {
			if(left & 1) Lazy[left] = h(Lazy[left], operator_);
			if(right & 1) Lazy[right - 1] = h(Lazy[right - 1], operator_);
			(left += 1) >>= 1;
			right >>= 1;
		}
		left = L0;
		right = R0;
		while(left > 1) {
			left >>= 1;
			Node[left] = f(g(Node[left << 1], Lazy[left << 1]), g(Node[left << 1 | 1], Lazy[left << 1 | 1]));
			Lazy[left] = e_unit;
		}
		while(right > 1) {
			right >>= 1;
			Node[right] = f(g(Node[right << 1], Lazy[right << 1]), g(Node[right << 1 | 1], Lazy[right << 1 | 1]));
			Lazy[right] = e_unit;
		}
	}

	//半開区間[a, b)の区間クエリ
	Monoid query(int left, int right) {  
		eval(left, right);
		Monoid a = Monoid_unit, b = Monoid_unit;
		left += n, right += n;
		while(left < right){
			if(left & 1) a = f(a, g(Node[left], Lazy[left]));
			if(right & 1) b = f(g(Node[right - 1], Lazy[right - 1]), b);
			(left += 1) >>= 1;
			right >>= 1;
		}
		return f(a, b);
	}

	Monoid operator[](int i) {
		return query(i, i + 1);
	}
};

int main(){
	LL(n, d, a);
	VEC(P, vec, n);
	V<ll> co;
	REP(i, n) co.pb(vec[i].first), co.pb(vec[i].first - d), co.pb(vec[i].first + d);
	auto t = press(co);
	map<ll, int> pr;
	REP(i, SZ(t)) pr[t[i]] = i; 
	V<ll> hp(SZ(t), 0);
	REP(i, n) hp[pr[vec[i].first]] += vec[i].second;
	debug(hp);
	auto f = [](ll x, ll y){return x + y;};
	LazySegmentTree<ll, ll> LST(hp, f, f, f, 0, 0);
	REP(i, SZ(t)) debug(LST[i]);
	ll res = 0;
	debug(t);
	REP(i, SZ(hp)){
		if(LST[i] <= 0) continue;
		ll k = divup(LST[i], (ll)a);
		res += k;
		int right = upper_bound(all(t), t[i] + 2 * d) - t.begin();
		debug(LST[i], i, right, k);
		LST.update(i, right, -k * a);
	}
	print(res);
}

Measured memory_bytes: 85880