#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
 
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
 
#define start_routine() int begtime = clock();
#define end_routine() int endtime = clock(); cerr << endl << "Time elapsed: " << (endtime - begtime)*1000/CLOCKS_PER_SEC << " ms"; return 0
#define speed() cin.tie(0), cout.tie(0), ios_base::sync_with_stdio(false)
// #define exit(a, b) return cout << a, b;
 
// debugger
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
    cout << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
    const char* comma = strchr(names + 1, ',');cout.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
}
#define debug(stuff) cout << #stuff << ": " << stuff <<endl
#define debugc(stuff) cout << #stuff << ": "; for(auto x: stuff) cout << x << " "; cout << endl;
// 
 
#define loop(i,a,b) for(ll i=a;i<b;i++)
#define all(v) v.begin(), v.end() 
 
#define print(stuff) cout << stuff << endl
#define printc(stuff) for(auto x: stuff) cout << x << " "; cout << endl;
#define printPrec(stuff) cout << fixed << setprecision(15) << stuff << endl;
#define len length
#define ret0 return 0
#define ret return 
 
 
#define ll long long
#define ld long double
#define fi first
#define endl '\n'
#define se second
#define pb push_back
#define mp make_pair
#define lb lower_bound
#define ub upper_bound
#define fill(ar, x) memset(ar, x, sizeof ar)
 
#define vl vector<ll> 
#define sl set<ll>
#define pll pair<ll, ll>
#define mll map<ll, ll> 
#define pq priority_queue<ll>
 
// typedef tree<ll,null_type,less<ll>,rb_tree_tag,
// tree_order_statistics_node_update> indexed_set;
 
#define inf (long long int) 1e18
#define eps 0.000001
#define mod 1000000007
#define mod1 998244353
#define MAXN (ll)2e5+5
#define N (1ll<<10)
#define pi 3.141592653589793238462643

ll t[4*MAXN], lazy[4*MAXN]={0};
ll h[MAXN], x[MAXN];

void build(ll node, ll start, ll end){
    if(start == end){
        t[node] = h[start];
        return ;
    }
    ll mid = (start + end) / 2;
    build(2*node, start, mid);
    build(2*node+1, mid+1, end);
    t[node] = t[2*node] + t[2*node+1]; 
}

void updateRange(ll node, ll start, ll end, ll l, ll r, ll val) {
    if(lazy[node] != 0) { 
        t[node] += (end - start + 1) * lazy[node];    
        if(start != end){
            lazy[2*node] += lazy[node];                  
            lazy[2*node+1] += lazy[node];                
        }
        lazy[node] = 0;                                  
    }
    if(start > end or start > r or end < l) {
        return ;
    }          
    if(start >= l and end <= r) {
        t[node] += (end - start + 1) * val;
        if(start != end) {
            lazy[2*node] += val;
            lazy[2*node+1] += val;
        }
        return;
    }
    ll mid = (start + end) / 2;
    updateRange(2*node, start, mid, l, r, val);        
    updateRange(2*node + 1, mid + 1, end, l, r, val);   
    t[node] = t[2*node] + t[2*node+1];       
}

ll queryRange(ll node, ll start, ll end, ll l, ll r) {
    if(lazy[node] != 0) {
        t[node] += (end - start + 1) * lazy[node];            
        if(start != end) {
            lazy[2*node] += lazy[node];        
            lazy[2*node+1] += lazy[node];   
        }
        lazy[node] = 0;                
    }
    if(start > end or start > r or end < l) {
        return 0;       
    }
    if(start >= l and end <= r) {           
        return t[node];
    }
    ll mid = (start + end) / 2;
    ll p1 = queryRange(2*node, start, mid, l, r);         
    ll p2 = queryRange(2*node + 1, mid + 1, end, l, r);
    return (p1 + p2);
}

ll ceil(ll a,ll b){
    return a/b+(a%b!=0);
}
void solve(){
    ll n, d, a;
    cin>>n>>d>>a;

    pll p[n];
    loop(i,0,n){
        cin>>p[i].fi>>p[i].se;
    }
    sort(p, p+n);
    loop(i,0,n){
        x[i] = p[i].fi;
        h[i] = p[i].se;
    }
    build(1, 0, n-1);
    ll ans = 0;
    for(ll i=0; i<n; i++){
        ll qqq = queryRange(1, 0, n-1, i, i);
        // trace(i, qqq);
        if(qqq < 0) continue; 
        ll val = ceil(qqq, a);
        ans += ceil(qqq, a);
        ll idx = ub(x, x+n, x[i]+2*d) - x;
        idx--;
        updateRange(1, 0, n-1, i, idx, -val*a);
    }
    print(ans);
}
 
int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
 
    ll t = 1;
    // cin>>t;
    while(t--){
        solve();
    }
      
}


Measured memory_bytes: 17664