//#pragma GCC optimize ("Ofast")
//#pragma GCC optimize ("unroll-loops")
//#pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
#define pb push_back
#define F first
#define S second
#define ins insert
#define mp make_pair
#define fo(i, n1, n, x) for(int i = n1; i <= n; i += x)
#define foo(i, n, n1, x) for(int i = n; i >= n1; i -= x)
#define bit __builtin_popcount
#define md (l + ((r - l) / 2))
#define all(x) x.begin(),x.end()
#define eb emplace_back
#define ub upper_bound
#define lb lower_bound
#define ios ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define file(s) if (fopen(s".in", "r")) freopen(s".in", "r", stdin), freopen(s".out", "w", stdout)

using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;


using ll = long long;

#define int ll


const int N = 3e5 + 11, mod = 1e9 + 7, mod2 = 998244353;
const int MAX = 1e5 + 11;
const int INF1 = 2e9 + 11;
const ll INF2 = 2e18 + 11;
const double INF3 = 1e8 + 11;
const int base = 500;
const int P = 31;
const int dx[] = {1, -1, 0, 0, 1, 1, -1, -1};
const int dy[] = {0, 0, 1, -1, 1, -1, 1, -1};
const double EPS = 1e-4;
const double PI = acos(-1.0);


template<typename T> using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }


typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
typedef vector <int> vi;


mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int n, d, val, ans, Right[N], t[N * 4], z[N * 4];
pii a[N];
void push(int v, int l, int r) {
    if (!z[v]) return;
    if (l != r) z[v + v] += z[v], z[v + v + 1] += z[v];
    t[v] += z[v];
    z[v] = 0;
}
int get(int v, int l, int r, int left, int righ) {
    push(v, l, r);
    if (left > r || righ < l) return 0;
    if (left <= l and r <= righ) return max(0ll, t[v]);
    push(v, l, r);
    return get(v + v, l, md, left, righ) + get(v + v + 1, md + 1, r, left ,righ);
}
void upd(int v, int l, int r, int left, int righ, int vl) {
    push(v, l, r);
    if (left > r || righ < l) return;
    if (left <= l and r <= righ) {
        z[v] += vl;
        push(v, l, r);
        return;
    }
    push(v, l, r);
    upd(v + v, l, md, left, righ, vl);
    upd(v + v + 1, md + 1, r, left, righ, vl);
    push(v, l, r);
}
main() {
    file("threesum");
    ios;
    cin >> n >> d >> val;
    fo(i, 1, n, 1) cin >> a[i].F >> a[i].S;
    sort(a + 1, a + n + 1);
    fo(i, 1, n, 1) upd(1, 1, n, i, i, a[i].S);
    if (n == 1) return !(cout << (a[1].S + val - 1) / val);
    int id = 1;
    fo(i, 2, n, 1) {
        while (a[id].F + d + d < a[i].F) {
            Right[id] = i;
            ++id;
        }
    }
    while (id <= n) Right[id] = n + 1, ++id;
    fo(i, 1, n, 1) {
        int y = max(0ll, (get(1, 1, n, i, i) + val - 1) / val);
        ans += y;
        upd(1, 1, n, i, Right[i] - 1, -(y * val));
    }
    cout << ans;
    cerr << "\nTime elapsed: " << (clock() + 0.0) / CLOCKS_PER_SEC;
    return 0;
}
/**

*/


Measured memory_bytes: 19072