#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using P = pair<ll, ll>;
using Pld = pair<ld, ld>;
using Vec = vector<ll>;
using VecP = vector<P>;
using VecB = vector<bool>;
using VecC = vector<char>;
using VecD = vector<ld>;
using VecS = vector<string>;
using VecVec = vector<Vec>;
using Graph = vector<VecP>;
template <typename T>
using Vec1 = vector<T>;
template <typename T>
using Vec2 = vector<Vec1<T> >;
#define REP(i, m, n) for(ll (i) = (m); (i) < (n); ++(i))
#define REPN(i, m, n) for(ll (i) = (m); (i) <= (n); ++(i))
#define REPR(i, m, n) for(ll (i) = (m)-1; (i) >= (n); --(i))
#define REPNR(i, m, n) for(ll (i) = (m); (i) >= (n); --(i))
#define rep(i, n) REP(i, 0, n)
#define repn(i, n) REPN(i, 1, n)
#define repr(i, n) REPR(i, n, 0)
#define repnr(i, n) REPNR(i, n, 1)
#define all(s) (s).begin(), (s).end()
#define pb push_back
#define mp make_pair
#define fs first
#define sc second
template <typename T>
bool chmax(T &a, const T& b){if(a < b){a = b; return true;} return false;}
template <typename T>
bool chmin(T &a, const T& b){if(a > b){a = b; return true;} return false;}
template <typename T>
void co(const T n){cout << n << endl;}
template <typename T>
void cosp(const T n){cout << n << ' ';}
template <typename T>
void co(const Vec &v){for(ll i : v) cosp(i); cout << endl;}
template <typename T>
void co(initializer_list<T> v){for(T i : v) cosp(i); cout << endl;}
void sonic(){ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);}
void setp(const ll n){cout << fixed << setprecision(n);}
const ll INF = 1e9+1;
const ll LINF = 1e18+1;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const ld PI = acos(-1);
const ld EPS = 1e-11;

//range : 0 ~ n-1
template <typename T>
struct LasySegmentTree{
	using F = function<T(T, T)>;
	T N;
	T d;
	F f;
	Vec1<T> data;
	Vec1<T> lazy;

	LasySegmentTree(T n, T d, F f) : f(f), d(d){
		init(n);
	}

	void init(ll n){
		N = 1;
		while(N < n) N <<= 1;
		data.assign(N*2, d);
		lazy.assign(N*2, 0);
	}

	void build(Vec1<T> v){
		rep(i, v.size()) data[N+i] = v[i];
		repnr(i, N-1) data[i] = f(data[i*2], data[i*2+1]);
	}

	void eval(T k){
		if(lazy[k] == 0) return;
		if(k < N){
			lazy[k*2] += lazy[k];
			lazy[k*2+1] += lazy[k];
		}
		data[k] += lazy[k];
		lazy[k] = 0;
	}

	T add(T a, T x){return add(a, a+1, x, 1, 0, N);}
	T add(T a, T b, T x){return add(a, b, x, 1, 0, N);}
	T add(T a, T b, T x, T k, T l, T r){
		eval(k);
		if(r <= a || b <= l) return data[k];
		if(a <= l && r <= b){
			lazy[k] += x;
			return data[k]+lazy[k];
		}
		T m = (l+r)/2;
		return data[k] = f(add(a, b, x, k*2, l, m), add(a, b, x, k*2+1, m, r));
	}

	T query(T a, T b){return query(a, b, 1, 0, N);}
	T query(T a, T b, T k, T l, T r){
		eval(k);
		if(r <= a || b <= l) return d;
		if(a <= l && r <= b) return data[k];
		T m = (l+r)/2;
		return f(query(a, b, k*2, l, m), query(a, b, k*2+1, m, r));
	}
};

int main(void){
	ll n, d, a;
	cin >> n >> d >> a;
	VecP p(n);
	rep(i, n) cin >> p[i].fs >> p[i].sc;
	sort(all(p));
	Vec x(n), h(n);
	rep(i, n){
		x[i] = p[i].fs;
		h[i] = p[i].sc;
	}

	LasySegmentTree<ll> lst(n, -LINF, [](ll a, ll b){return max(a, b);});
	lst.build(h);

	ll ans = 0;
	rep(i, n){
		ll b = lst.query(i, i+1);
		if(b <= 0) continue;
		ll c = (b-1)/a+1;
		ans += c;
		ll pos = upper_bound(all(x), x[i]+2*d)-x.begin();
		lst.add(i, pos, -c*a);
	}
	co(ans);

	return 0;
}


Measured memory_bytes: 16256