#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <numeric>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
typedef long long int ll;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; PPPPP(__VA_ARGS__); cerr << endl; } while(false)
template<typename T> void PPPPP(T t) { cerr << t; }
template<typename T, typename... S> void PPPPP(T t, S... s) { cerr << t << ", "; PPPPP(s...); }
#else
#define dump(...)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T>
bool chmin(T &a, T b) { if (a > b) {a = b; return true; } return false;}
template<typename T>
bool chmax(T &a, T b) { if (a < b) {a = b; return true; } return false;}
// clang-format on

#include <functional>
template<typename T>
class SegmentTreeAllOne {
    using Func = function<T(T, T)>;

public:
    vector<T> data;
    int n;
    T init;
    Func update_func;
    SegmentTreeAllOne(int _n, T _init, Func up) {
        init = _init;
        update_func = up;
        for (n = 1; n < _n; n *= 2)
            ;
        data.resize(2 * n - 1, init);
    }
    void update(int l, int r, T val) {
        for (l += n - 1, r += n - 1; l < r; l = l / 2, r = (r - 1) / 2) {
            if (!(l & 1)) {
                data[l] = update_func(data[l], val);
            }
            if (!(r & 1)) {
                data[r - 1] = update_func(data[r - 1], val);
            }
        }
    }
    T query(int pos) {
        pos += n - 1;
        T res = data[pos];
        while (pos > 0) {
            pos = (pos - 1) / 2;
            res = update_func(res, data[pos]);
        }
        return res;
    }
};

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll n, d, a;
    cin >> n >> d >> a;
    vector<ll> x(n), h(n);
    REP(i, 0, n) {
        cin >> x[i] >> h[i];
    }
    vector<ll> xlist;
    REP(i, 0, n) {
        xlist.push_back(x[i]);
        REP(j, 1, 3) {
            xlist.push_back(x[i] - j * d);
            xlist.push_back(x[i] + j * d);
        }
    }
    sort(xlist.begin(), xlist.end());
    xlist.erase(unique(xlist.begin(), xlist.end()), xlist.end());

    vector<ll> px(n), ax(n), ppx(n), aax(n);
    REP(i, 0, n) {
        px[i] = lower_bound(xlist.begin(), xlist.end(), x[i] - d) - xlist.begin();
        ax[i] = lower_bound(xlist.begin(), xlist.end(), x[i] + d) - xlist.begin();
        ppx[i] = lower_bound(xlist.begin(), xlist.end(), x[i] - 2 * d) - xlist.begin();
        aax[i] = lower_bound(xlist.begin(), xlist.end(), x[i] + 2 * d) - xlist.begin();
        x[i] = lower_bound(xlist.begin(), xlist.end(), x[i]) - xlist.begin();
    }
    auto sum = [](ll t, ll s) {
        return t + s;
    };
    SegmentTreeAllOne<ll> segtree(5 * n + 1, 0LL, sum);

    vector<int> ord(n);
    iota(ord.begin(), ord.end(), 0);
    sort(ord.begin(), ord.end(), [&](int t, int s) {
        if (x[t] != x[s])
            return x[t] < x[s];
        else
            return h[t] < h[s];
    });

    ll cnt = 0;
    int p = 0;
    REP(i, 0, n) {
        ll res = h[ord[i]] - segtree.query(x[ord[i]]);
        dump(i, x[ord[i]], res);
        if (res <= 0) continue;
        while (p < n && ppx[ord[p]] <= x[ord[i]]) {
            p++;
        }
        ll ct = (res + a - 1) / a;
        dump(ct, ppx[ord[p - 1]], x[ord[p - 1]] + 1);
        cnt += ct;
        segtree.update(ppx[ord[p - 1]], x[ord[p - 1]] + 1, ct * a);
    }
    cout << cnt << endl;
    return 0;
}


Measured memory_bytes: 34664