#include <bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
#define chmax(x,y) x = max(x,y)
#define chmin(x,y) x = min(x,y)
using namespace std;
typedef long long ll;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> T;
const long long INF = 1LL<<60;
const int MOD = 1000000000+7;
#define rev(s) (string((s).rbegin(), (s).rend()))
template < typename T > inline string toString( const T &a ) { ostringstream oss; oss << a; return oss.str(); };
// cout << fixed << setprecision(10) << ans << endl;
// *min_element(c + l, c + r) *max_element(c + l, c + r)
// int dx[8]={1,1,0,-1,-1,-1,0,1};
// int dy[8]={0,1,1,1,0,-1,-1,-1};
// int dx[4]={1,0,-1,0};
// int dy[4]={0,1,0,-1};
// struct Edge {
//   int to, id;
//   Edge(int to, int id): to(to), id(id) {}
// };

#define N (1 << 19)

class SegmentTree {
  static const ll inf = 1e18;
  struct Node {
    Node *left, *right;
    ll max_v, smax_v, max_c;
    ll min_v, smin_v, min_c;
    ll sum;
    ll len, ladd, lval;

    Node() : left(0), right(0), ladd(0), lval(inf) {}

    void init(ll x) {
      max_v = min_v = sum = x;
      smax_v = -inf; smin_v = inf;
      max_c = min_c = 1;
    }

    void init_empty() {
      max_v = smax_v = -inf;
      min_v = smin_v = inf;
      max_c = min_c = 0;
    }

    void update_max(ll x) {
      sum += (x - max_v) * max_c;

      if(max_v == min_v) {
        max_v = min_v = x;
      } else if(max_v == smin_v) {
        max_v = smin_v = x;
      } else {
        max_v = x;
      }

      if(lval != inf && x < lval) {
        lval = x;
      }
    }

    void update_min(ll x) {
      sum += (x - min_v) * min_c;

      if(max_v == min_v) {
        max_v = min_v = x;
      } else if(max_v == smin_v) {
        min_v = smax_v = x;
      } else {
        min_v = x;
      }

      if(lval != inf && lval < x) {
        lval = x;
      }
    }

    void addall(ll x) {
      max_v += x;
      if(smax_v != -inf) smax_v += x;
      min_v += x;
      if(smin_v != inf) smin_v += x;

      sum += len * x;
      if(lval != inf) {
        lval += x;
      } else {
        ladd += x;
      }
    }

    void updateall(ll x) {
      max_v = min_v = x;
      smax_v = -inf; smin_v = inf;
      max_c = min_c = len;

      sum = len * x;
      lval = x; ladd = 0;
    }

    void push() {

      if(lval != inf) {
        left->updateall(lval);
        right->updateall(lval);
        lval = inf;
        return;
      }

      if(ladd != 0) {
        left->addall(ladd);
        right->addall(ladd);
        ladd = 0;
      }

      if(max_v < left->max_v) {
        left->update_max(max_v);
      }
      if(left->min_v < min_v) {
        left->update_min(min_v);
      }

      if(max_v < right->max_v) {
        right->update_max(max_v);
      }
      if(right->min_v < min_v) {
        right->update_min(min_v);
      }
    }

    void update() {
      sum = left->sum + right->sum;

      if(left->max_v < right->max_v) {
        max_v = right->max_v;
        max_c = right->max_c;
        smax_v = max(left->max_v, right->smax_v);
      } else if(left->max_v > right->max_v) {
        max_v = left->max_v;
        max_c = left->max_c;
        smax_v = max(left->smax_v, right->max_v);
      } else {
        max_v = left->max_v;
        max_c = left->max_c + right->max_c;
        smax_v = max(left->smax_v, right->smax_v);
      }

      if(left->min_v < right->min_v) {
        min_v = left->min_v;
        min_c = left->min_c;
        smin_v = min(left->smin_v, right->min_v);
      } else if(left->min_v > right->min_v) {
        min_v = right->min_v;
        min_c = right->min_c;
        smin_v = min(left->min_v, right->smin_v);
      } else {
        min_v = left->min_v;
        min_c = left->min_c + right->min_c;
        smin_v = min(left->smin_v, right->smin_v);
      }
    }
  };

  int n, n0;
  Node *root;

  void _update_min(ll x, int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a || nd->max_v <= x) {
      return;
    }
    if(a <= l && r <= b && nd->smax_v < x) {
      nd->update_max(x);
      return;
    }

    nd->push();
    _update_min(x, a, b, nd->left, l, (l+r)/2);
    _update_min(x, a, b, nd->right, (l+r)/2, r);
    nd->update();
  }

  void _update_max(ll x, int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a || x <= nd->min_v) {
      return;
    }
    if(a <= l && r <= b && x < nd->smin_v) {
      nd->update_min(x);
      return;
    }

    nd->push();
    _update_max(x, a, b, nd->left, l, (l+r)/2);
    _update_max(x, a, b, nd->right, (l+r)/2, r);
    nd->update();
  }

  void _add_val(ll x, int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a) {
      return;
    }
    if(a <= l && r <= b) {
      nd->addall(x);
      return;
    }

    nd->push();
    _add_val(x, a, b, nd->left, l, (l+r)/2);
    _add_val(x, a, b, nd->right, (l+r)/2, r);
    nd->update();
  }

  void _update_val(ll x, int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a) {
      return;
    }
    if(a <= l && r <= b) {
      nd->updateall(x);
      return;
    }

    nd->push();
    _update_val(x, a, b, nd->left, l, (l+r)/2);
    _update_val(x, a, b, nd->right, (l+r)/2, r);
    nd->update();
  }

  ll _query_max(int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a) {
      return -inf;
    }
    if(a <= l && r <= b) {
      return nd->max_v;
    }
    nd->push();
    ll lv = _query_max(a, b, nd->left, l, (l+r)/2);
    ll rv = _query_max(a, b, nd->right, (l+r)/2, r);
    return max(lv, rv);
  }

  ll _query_min(int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a) {
      return inf;
    }
    if(a <= l && r <= b) {
      return nd->min_v;
    }
    nd->push();
    ll lv = _query_min(a, b, nd->left, l, (l+r)/2);
    ll rv = _query_min(a, b, nd->right, (l+r)/2, r);
    return min(lv, rv);
  }

  ll _query_sum(int a, int b, Node *nd, int l, int r) {
    if(b <= l || r <= a) {
      return 0;
    }
    if(a <= l && r <= b) {
      return nd->sum;
    }
    nd->push();
    ll lv = _query_sum(a, b, nd->left, l, (l+r)/2);
    ll rv = _query_sum(a, b, nd->right, (l+r)/2, r);
    return lv + rv;
  }

public:
  SegmentTree(int n, ll *a) : n(n) {
    n0 = 1;
    while(n0 < n) n0 <<= 1;

    Node *nds = new Node[2*n0];
    root = nds;

    nds[0].len = n0;
    for(int i=0; i<n0-1; ++i) {
      nds[i].left = &nds[2*i+1];
      nds[i].right = &nds[2*i+2];
      nds[2*i+1].len = nds[2*i+2].len = (nds[i].len >> 1);
    }

    for(int i=0; i<n; ++i) nds[n0-1+i].init(a[i]);
    for(int i=n; i<n0; ++i) nds[n0-1+i].init_empty();
    for(int i=n0-2; i>=0; i--) nds[i].update();
  }

  void update_min(int a, int b, ll x) {
    _update_min(x, a, b, root, 0, n0);
  }

  void update_max(int a, int b, ll x) {
    _update_max(x, a, b, root, 0, n0);
  }

  void add_val(int a, int b, ll x) {
    _add_val(x, a, b, root, 0, n0);
  }

  void update_val(int a, int b, ll x) {
    _update_val(x, a, b, root, 0, n0);
  }

  ll query_max(int a, int b) {
    return _query_max(a, b, root, 0, n0);
  }

  ll query_min(int a, int b) {
    return _query_min(a, b, root, 0, n0);
  }

  ll query_sum(int a, int b) {
    return _query_sum(a, b, root, 0, n0);
  }
};

ll vec[N];

int main() {
  ll n,d,a;cin>>n>>d>>a;
  vector<P> xh(n);
  rep(i,n) cin>>xh[i].first>>xh[i].second;
  ll ans = 0;
  sort(xh.begin(),xh.end());
  SegmentTree tree(n,vec);
  
  rep(i,n) {
    ll num = tree.query_sum(i,i+1);
    ll gap = xh[i].second - num * a;
    if(gap <= 0) continue;
    ll need = (gap-1)/a + 1;
    ans += need;
    ll plc = upper_bound(xh.begin(),xh.end(),P(xh[i].first + 2 * d,1000000001)) - xh.begin();
    tree.add_val(i,plc,need);
  }
  cout<<ans<<endl;
}


Measured memory_bytes: 55716