#include<bits/stdc++.h>

#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define xx first
#define yy second
#define sci(n) scanf("%d",&n)
#define scii(n,m) scanf("%d%d",&n,&m)
#define sciii(n,m,w) scanf("%d%d%d",&n,&m,&w)
#define scl(n) scanf("%lld",&n)
#define scll(n,m) scanf("%lld%lld",&n,&m)
#define sclll(n,m,w) scanf("%lld%lld%lld",&n,&m,&w)
#define pf(a)   printf("%d\n",a)
#define CASE(a) printf("Case %d: ",a)
#define dbg(i) printf("yo %d\n", i)
#define endl '\n'
#define pi acos(-1)
#define mem(a,b) memset(a,b,sizeof(a))
#define SQR(a) (a)*(a)
#define all(v) v.begin(),v.end()
#define pb push_back
#define pri priority_queue<int>
#define rev_pri priority_queue<int,vector<int>,greater<int> >
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);
#define mod 1000000007
#define inf INT_MAX
#define eps 1e-9

using namespace std;

//int dx[] = {0,1,0,-1,1,1,-1,-1};
//int dy[] = {1,0,-1,0,1,-1,-1,1};

//ll ncr(ll n,ll r){if(n==r)return 1;if(r==1)return n;if(dp[n][r]!=-1)return dp[n][r];return dp[n][r]=ncr(n-1,r)+ncr(n-1,r-1);}

// bit manipulations

//bool checkbit(int mask,int bit){return mask & (1<<bit);}
//int setbit(int mask,int bit){ return mask  (1<<bit) ; }
//int clearbit(int mask,int bit){return mask & ~(1<<bit);}
//int togglebit(int mask,int bit){return mask ^ (1<<bit);}

template <typename T> T BigMod (T b,T p,T m){if (p == 0) return 1;if (p%2 == 0){T s = BigMod(b,p/2,m);return ((s%m)*(s%m))%m;}return ((b%m)*(BigMod(b,p-1,m)%m))%m;}
template <typename T> T ModInv (T b,T m){return BigMod(b,m-2,m);}
template <typename T> T in(){char ch;T n = 0;bool ng = false;while (1){ch = getchar();if (ch == '-'){ng = true;ch = getchar();break;}if (ch>='0' && ch<='9')     break;}while (1){n = n*10 + (ch - '0');ch = getchar();if (ch<'0' || ch>'9')   break;}return (ng?-n:n);}
template <typename T> T POW(T B,T P){ if(P==0) return 1; if(P&1) return B*POW(B,P-1);  else return SQR(POW(B,P/2));}
template <typename T> T Bigmod(T b,T p,T m){ if(p==0) return 1; else if (!(p&1)) return SQR(Bigmod(b,p/2,m)) % m;else return ((b % m) * Bigmod(b,p-1,m)) % m;}
template <typename T> T Dis(T x1,T y1,T x2, T y2){return sqrt( SQR(x1-x2) + SQR(y1-y2) );}
template <typename T> T Angle(T x1,T y1,T x2, T y2){ return atan( double(y1-y2) / double(x1-x2));}
template <typename T> T DIFF(T a,T b) { T d = a-b;if(d<0)return -d;else return d;}
template <typename T> T ABS(T a) {if(a<0)return -a;else return a;}
template <typename T> T gcd(T a,T b){if(a<0)return gcd(-a,b);if(b<0)return gcd(a,-b);return (b==0)?a:gcd(b,a%b);}
template <typename T> T lcm(T a,T b) {if(a<0)return lcm(-a,b);if(b<0)return lcm(a,-b);return a*(b/gcd(a,b));}
template <typename T> T euclide(T a,T b,T &x,T &y) {if(a<0){T d=euclide(-a,b,x,y);x=-x;return d;}   if(b<0){T d=euclide(a,-b,x,y);y=-y;return d;}   if(b==0){x=1;y=0;return a;}else{T d=euclide(b,a%b,x,y);T t=x;x=y;y=t-(a/b)*y;return d;}}
template <typename T> void ia (T a[],int n){for (int i=0; i<n; i++) cin >> a[i];}
template <typename T> void pa (T a[],int n){for (int i=0; i<n-1; i++) cout << a[i] << " ";cout << a[n-1] << endl;}
template <typename T> ll isLeft(T a,T b,T c) { return (a.x-b.x)*(b.y-c.y)-(b.x-c.x)*(a.y-b.y);}

#define mxn 200005
ll n , d , a;
vector<pair<ll,ll> > v;
vector<ll> arr;

struct info{
     ll sum;
     ll lazy;
}seg[4 * mxn + 5];


void update(int node,int b,int e,int i, int j, ll x){

     if(b > j || e < i) return;
     if(b >= i && e <= j){
        seg[node].sum  += (e - b + 1) * x;
        seg[node].lazy += x;
        return;
     }

     int left = 2 * node;
     int right = left + 1;
     int mid = (b + e) / 2;


     if(seg[node].lazy != 0){

        seg[left].lazy += seg[node].lazy;
        seg[right].lazy += seg[node].lazy;

        seg[left].sum += (mid - b + 1) * seg[node].lazy;
        seg[right].sum += (e - mid) * seg[node].lazy;
        seg[node].lazy = 0;
     }

     update(left,b,mid,i,j,x);
     update(right,mid + 1,e,i,j,x);

     seg[node].sum = seg[left].sum + seg[right].sum;

}

ll query(int node,int b,int e,int i, int j){

   if(b > j || e < i) return 0;
   if(b >= i && e <= j){
        return seg[node].sum;
   }

   int left = node * 2;
   int right = left + 1;
   int mid = (b + e) / 2;


     if(seg[node].lazy !=0){

        seg[left].lazy += seg[node].lazy;
        seg[right].lazy += seg[node].lazy;


        seg[left].sum += (mid - b + 1) * seg[node].lazy;
        seg[right].sum += (e - mid) * seg[node].lazy;
        seg[node].lazy = 0;
     }

   ll x = query(left,b,mid,i,j);
   ll y = query(right,mid + 1,e,i,j);

   return x + y;
}


int main(){

      IOS;
      cin >> n >> d >> a;

      for(int i = 0;i < n;i++){
        ll x , h;
        cin >> x >> h;
        v.pb({x,h});
      }


      sort(all(v));
      for(int i = 0;i < n;i++){
          arr.pb(v[i].xx);
          update(1,0,n-1,i,i,v[i].yy);
      }

      ll cnt = 0;

      for(int i = 0;i < n;i++){

         ll temp = query(1,0,n - 1,i,i);
         //cout << temp <<endl;
         if(temp <= 0) continue;
         ll bar = temp / a;
         if(temp % a) bar++;

         ll pos = upper_bound(all(arr),arr[i] + 2 * d) - arr.begin();
         pos--;
         //cout << pos << endl;


         cnt += bar;
         //cout << bar << endl;
         update(1,0,n-1,i,pos,-(bar * a));


      }

      cout << cnt <<endl;














return 0;}













Measured memory_bytes: 17900