#include<bits/stdc++.h>
#define ios std::ios::sync_with_stdio(false)
#define sd(n) scanf("%d",&n)
#define sdd(n,m) scanf("%d%d",&n,&m)
#define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define pd(n) printf("%d\n", (n))
#define pdd(n,m) printf("%d %d\n", n, m)
#define pld(n) printf("%lld\n", n)
#define pldd(n,m) printf("%lld %lld\n", n, m)
#define sld(n) scanf("%lld",&n)
#define sldd(n,m) scanf("%lld%lld",&n,&m)
#define slddd(n,m,k) scanf("%lld%lld%lld",&n,&m,&k)
#define sf(n) scanf("%lf",&n)
#define sff(n,m) scanf("%lf%lf",&n,&m)
#define sfff(n,m,k) scanf("%lf%lf%lf",&n,&m,&k)
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,n,a) for (int i=n;i>=a;i--)
#define mm(a,n) memset(a, n, sizeof(a))
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define il inline
#define ll long long
#define lson rt << 1
#define rson rt << 1 | 1
#define MOD 1000000007
#define pi 3.14159265358979323
#define debug(x) 			  cout <<#x<<": "<<x<<endl;
#define debug2(x, y)          cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<endl;
#define debug3(x, y, z)       cout <<#x<<": "<<x<<" | "<<#y<<": "<<y<<" | "<<#z<<": "<<z<<endl;
#define debug4(a, b, c, d)    cout <<#a<<": "<<a<<" | "<<#b<<": "<<b<<" | "<<#c<<": "<<c<<" | "<<#d<<": "<<d<<endl;
using namespace std;
const ll INF (0x3f3f3f3f3f3f3f3fll);
const int inf (0x3f3f3f3f);
template<typename T>void read(T &res)
{
	bool flag=false;
	char ch;
	while(!isdigit(ch=getchar()))(ch=='-')&&(flag=true);
	for(res=ch-48; isdigit(ch=getchar()); res=(res<<1)+(res<<3)+ch - 48);
	flag&&(res=-res);
}
template<typename T>void Out(T x)
{
	if(x<0)putchar('-'),x=-x;
	if(x>9)Out(x/10);
	putchar(x%10+'0');
}
ll gcd(ll a,ll b)
{
	return b?gcd(b,a%b):a;
}
ll lcm(ll a,ll b)
{
	return a*b/gcd(a,b);
}
ll pow_mod(ll x,ll n,ll mod)
{
	ll res=1;
	while(n)
	{
		if(n&1)res=res*x%mod;
		x=x*x%mod;
		n>>=1;
	}
	return res;
}
ll fact_pow(ll n,ll p)
{
	ll res=0;
	while(n)
	{
		n/=p;
		res+=n;
	}
	return res;
}
ll mult(ll a,ll b,ll p)
{
	a%=p;
	b%=p;
	ll r=0,v=a;
	while(b)
	{
		if(b&1)
		{
			r+=v;
			if(r>p)r-=p;
		}
		v<<=1;
		if(v>p)v-=p;
		b>>=1;
	}
	return r;
}
ll quick_pow(ll a,ll b,ll p)
{
	ll r=1,v=a%p;
	while(b)
	{
		if(b&1)r=mult(r,v,p);
		v=mult(v,v,p);
		b>>=1;
	}
	return r;
}
bool CH(ll a,ll n,ll x,ll t)
{
	ll r=quick_pow(a,x,n);
	ll z=r;
	for(ll i=1; i<=t; i++)
	{
		r=mult(r,r,n);
		if(r==1&&z!=1&&z!=n-1)return true;
		z=r;
	}
	return r!=1;
}
bool Miller_Rabin(ll n)
{
	if(n<2)return false;
	if(n==2)return true;
	if(!(n&1))return false;
	ll x=n-1,t=0;
	while(!(x&1))
	{
		x>>=1;
		t++;
	}
	srand(time(NULL));
	ll o=8;
	for(ll i=0; i<o; i++)
	{
		ll a=rand()%(n-1)+1;
		if(CH(a,n,x,t))return false;
	}
	return true;
}

int prime[100000],minprime[100000];
void euler(int n)
{
	int c=0,i,j;
	for(i=2; i<=n; i++)
	{
		if(!minprime[i])prime[++c]=i,minprime[i]=i;
		for(j=1; j<=c&&i*prime[j]<=n; j++)
		{
			minprime[i*prime[j]]=prime[j];
			if(i%prime[j]==0)break;
		}
	}
}
const int N = 2e5 + 10;
struct Tree
{
	ll l,r,sum,lazy,maxn,minn;
} tree[2000000];
il void push_up(ll rt)
{
	tree[rt].sum=tree[rt<<1].sum+tree[rt<<1|1].sum;
	tree[rt].maxn=max(tree[rt<<1].maxn,tree[rt<<1|1].maxn);
	tree[rt].minn=min(tree[rt<<1].minn,tree[rt<<1|1].minn);
}
il void push_down(ll rt , ll length)
{
	if(tree[rt].lazy)
	{
		tree[rt<<1].lazy+=tree[rt].lazy;
		tree[rt<<1|1].lazy+=tree[rt].lazy;
		tree[rt<<1].sum+=(length-(length>>1))*tree[rt].lazy;
		tree[rt<<1|1].sum+=(length>>1)*tree[rt].lazy;
		tree[rt<<1].minn+=tree[rt].lazy;
		tree[rt<<1|1].minn+=tree[rt].lazy;
		tree[rt<<1].maxn+=tree[rt].lazy;
		tree[rt<<1|1].maxn+=tree[rt].lazy;
		tree[rt].lazy=0;
	}
}
il void build(ll l , ll r , ll rt , ll *aa)
{
	tree[rt].lazy=0;
	tree[rt].l=l;
	tree[rt].r=r;
	if(l==r)
	{
		tree[rt].sum=aa[l];
		tree[rt].minn=tree[rt].sum;
		tree[rt].maxn=tree[rt].sum;
		return;
	}
	ll mid=(l+r)>>1;
	build(l,mid,rt<<1,aa);
	build(mid+1,r,rt<<1|1,aa);
	push_up(rt);
}
il void update_range(ll L , ll R , ll key , ll rt)
{
	if(tree[rt].r<L||tree[rt].l>R)return;
	if(L<=tree[rt].l&&R>=tree[rt].r)
	{
		tree[rt].sum+=(tree[rt].r-tree[rt].l+1)*key;
		tree[rt].minn+=key;
		tree[rt].maxn+=key;
		tree[rt].lazy+=key;
		return;
	}
	push_down(rt,tree[rt].r-tree[rt].l+1);
	ll mid=(tree[rt].r+tree[rt].l)>>1;
	if(L<=mid)update_range(L,R,key,rt << 1);
	if(R>mid)update_range(L,R,key,rt << 1 | 1);
	push_up(rt);
}
il ll query_range(ll L, ll R, ll rt)
{
	if(L<=tree[rt].l&&R>=tree[rt].r)
	{
		return tree[rt].sum;
	}
	push_down(rt,tree[rt].r-tree[rt].l+1);
	ll mid=(tree[rt].r+tree[rt].l)>>1;
	ll ans=0;
	if(L<=mid)ans+=query_range(L,R,rt << 1);
	if(R>mid)ans+=query_range(L,R,rt << 1 | 1);
	return ans;
}
il ll query_min(ll L,ll R,ll rt)
{
	if(L<=tree[rt].l&&R>=tree[rt].r)
	{
		return tree[rt].minn;
	}
	push_down(rt,tree[rt].r-tree[rt].l+1);
	ll mid=(tree[rt].r+tree[rt].l)>>1;
	ll ans=(0x3f3f3f3f3f3f3f3fll);
	if(L<=mid)ans=min(ans,query_min(L,R,rt << 1));
	if(R>mid)ans=min(ans,query_min(L,R,rt << 1 | 1));
	return ans;
}
il ll query_max(ll L, ll R, ll rt)
{
	if(L<=tree[rt].l&&R>=tree[rt].r)
	{
		return tree[rt].maxn;
	}
	push_down(rt,tree[rt].r-tree[rt].l+1);
	ll mid=(tree[rt].r+tree[rt].l)>>1;
	ll ans=-(0x3f3f3f3f3f3f3f3fll);
	if(L<=mid)ans=max(ans,query_max(L,R,rt << 1));
	if(R>mid)ans=max(ans,query_max(L,R,rt << 1 | 1));
	return ans;
}
il ll query_range_size(ll L , ll R , ll rt , ll val)
{
	if(tree[rt].l == tree[rt].r)
		return tree[rt].l;
	push_down(rt,tree[rt].r-tree[rt].l+1);
	ll mid = tree[rt].l + tree[rt].r >> 1;
	if(tree[rt << 1].maxn > val)
		return query_range_size(L , R , rt << 1 , val);
	else if(tree[rt << 1 | 1].maxn > val)
		return query_range_size(L , R , rt << 1 | 1 , val);
	else 
		return -1;
}
string s;
struct node
{
	int x , h;
} a[N];
bool cmp(node a , node b)
{
	return a.x < b.x;
}
ll ha[N];
int main()
{
	ios;
	int n , d , c;
	cin >> n >> d >> c;
	rep(i , 1 , n)
	{
		cin >> a[i].x >> a[i].h;
		ha[i] = a[i].h;
	}
	sort(a + 1 , a + 1 + n , cmp);
	rep(i , 1 , n)
	ha[i] = a[i].h;
	build(1 , n , 1 , ha);
	int now = 1;
	ll ans = 0;
	a[n + 1].x = inf;
	while(1)
	{
		ll now = query_range_size(1 , n , 1 , 0);
		if(now == -1) break;
		int cnt = now ;
		while(a[now].x + d * 2 >= a[cnt].x  && cnt <= n) cnt ++ ;
		ll h = query_range(now , now , 1);
		ll cal = h / c;
		if(h % c) cal ++;
		update_range(now , cnt - 1 , -(cal * c) , 1);
		ans += cal; 
	}
	cout << ans << '\n';
	return 0;
}











