#pragma GCC optimize("Ofast","unroll-loops")
#pragma GCC push_options
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<bits/stdc++.h>
// #include <xmmintrin.h>
// #include <immintrin.h>
using namespace::std;
__attribute__((constructor))void init(){cin.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(15);}
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/priority_queue.hpp>
#include<ext/pb_ds/tag_and_trait.hpp>
// #include <boost/multiprecision/cpp_dec_float.hpp>
// #include <boost/multiprecision/cpp_int.hpp>
// namespace mp = boost::multiprecision;
// typedef mp::number<mp::cpp_dec_float<0>> cdouble;
// typedef mp::cpp_int cint;
template<typename T>using pbds=__gnu_pbds::tree<T,__gnu_pbds::null_type,less<T>,__gnu_pbds::rb_tree_tag,__gnu_pbds::tree_order_statistics_node_update>;
template<typename T>using pbds_map=__gnu_pbds::tree<T,T,less<T>,__gnu_pbds::rb_tree_tag,__gnu_pbds::tree_order_statistics_node_update>;
template<typename T,typename E>using hash_map=__gnu_pbds::gp_hash_table<T,E>;
template<typename T>using pqueue =__gnu_pbds::priority_queue<T, less<T>,__gnu_pbds::rc_binomial_heap_tag>;
typedef long long lint;
#define INF (1LL<<60)
#define IINF (1<<30)
#define EPS (1e-10)
#define MOD 1000000007LL
typedef vector<lint> vec;
typedef vector<vector<lint>> mat;
typedef vector<string> svec;
typedef vector<vector<string>> smat;
template<typename T>inline void numout(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i<INF/2?i:"INF";f=1;}cout<<endl;}
template<typename T>inline void numout2(T t){for(auto i:t)numout(i);}
template<typename T>inline void output(T t){bool f=0;for(auto i:t){cout<<(f?" ":"")<<i;f=1;}cout<<endl;}
template<typename T>inline void output2(T t){for(auto i:t)output(i);}
template<typename T>inline void _output(T t){bool f=0;for(lint i=0;i<t.size();i++){cout<<f?"":" "<<t[i];f=1;}cout<<endl;}
template<typename T>inline void _output2(T t){for(lint i=0;i<t.size();i++)output(t[i]);}
#define rep(i,n) for(lint i=0;i<lint(n);++i)
#define repi(i,a,b) for(lint i=lint(a);i<(lint)(b);++i)
#define rrep(i,n) for(lint i=lint(n)-1;i>=0;--i)
#define rrepi(i,a,b) for(lint i=lint(b)-1;i>=lint(a);--i)
#define irep(i) for(lint i=0;;++i)
#define all(n) begin(n),end(n)
#define dist(a,b,c,d) sqrt(pow(a-c,2)+pow(b-d,2))
inline lint gcd(lint A,lint B){return B?gcd(B,A%B):A;}
inline lint lcm(lint A,lint B){return A/gcd(A,B)*B;}
// inline cint cgcd(cint A,cint B){return B?cgcd(B,A%B):A;}
// inline cint clcm(cint A,cint B){return A/cgcd(A,B)*B;}
inline bool chmin(auto& s,const auto& t){bool res=s>t;s=min(s,t);return res;}
inline bool chmax(auto& s,const auto& t){bool res=s<t;s=max(s,t);return res;}
const vector<lint> dx={1,0,-1,0,1,1,-1,-1};
const vector<lint> dy={0,1,0,-1,1,-1,1,-1};
#define SUM(v) accumulate(all(v),0LL)
auto call=[&](auto f,auto... args){return f(f,args...);};

template<typename T>
class dual_segment{
	struct node;
	using np=node*;
	using lint=long long;
	struct node{
		T val;
		np ch[2]={nullptr,nullptr};
		node(T val):val(val){}
	};
	np root=nullptr;
	lint n=1,sz;
	T e;
	function<T(T,T)>f;
	public:
	dual_segment(lint sz,T e,function<T(T,T)>f):sz(sz),e(e),f(f){while(n<sz)n<<=1;}
	inline void set(lint l,lint r,T x){set(l,r,x,-n,n,root);}
	inline T get(lint x){return get(x,-n,n,root);}
	private:
	void eval(np& t){
		if(t->val==e)return;
		if(!t->ch[0])t->ch[0]=new node(e);
		if(!t->ch[1])t->ch[1]=new node(e);
		t->ch[0]->val=f(t->ch[0]->val,t->val);
		t->ch[1]->val=f(t->ch[1]->val,t->val);
		t->val=e;
	}
	void set(lint a,lint b,T x,lint l,lint r,np& t){
        if(!t)t=new node(e);
		if(r-l>1)eval(t);
		if(r<=a||b<=l)return;
		else if(a<=l&&r<=b)t->val=f(t->val,x);
	    else if(r-l>1){
			set(a,b,x,l,(l+r)/2,t->ch[0]);
			set(a,b,x,(l+r)/2,r,t->ch[1]);
		}
	}
	T get(lint x,lint l,lint r,np& t){
        if(!t)t=new node(e);
		if(r-l>1)eval(t);
		if(x<l||r<=x)return e;
        else if(r-l==1){
            return t->val;
        }
		else return f(get(x,l,(l+r)/2,t->ch[0]),get(x,(l+r)/2,r,t->ch[1]));
	}
};

int main(){
    lint n,d,a;
    cin>>n>>d>>a;
    vector<pair<lint,lint>> v(n);
    rep(i,n)cin>>v[i].first>>v[i].second;
    sort(all(v));
    dual_segment<lint> seg(n,0,[](auto a,auto b){return a+b;});
    lint ans=0;
    rep(i,n){
        lint cnt=0;
        if(v[i].second-seg.get(i)>0)cnt=(v[i].second-seg.get(i)-1)/a+1;
        ans+=cnt;
        lint range=(upper_bound(all(v),make_pair(v[i].first+2*d+1,-1LL))-v.begin());
        seg.set(i,range,a*cnt);
    }
    cout<<ans<<endl;
}

Measured memory_bytes: 15872