Language: C++

#include<bits/stdc++.h> 
using namespace std;

#define ll long long int
#define mp make_pair 
#define pb push_back
#define fast  ios_base::sync_with_stdio(false);cin.tie(0);
#define ff first
#define ss second
#define MOD  1000000007
#define ll_MAX 922337203685477999
#define endl "\n"
inline ll absdiff(ll a,ll b) {return (a>b)?a-b:b-a;}
ll fast_expo(ll x,ll p){if(p==0) return 1;
else if(p%2==0){ ll t=fast_expo(x,p/2)%MOD;return (t*t)%MOD;} else return (x*(fast_expo(x,p-1))%MOD)%MOD;}
ll gcd(ll a,ll b){if(a==0||b==0) return a+b;  else return gcd(b%a,a); }

ll Stree[1000000],lazy[1000000];


void Build(ll pos,ll s,ll e,vector<pair<ll,ll>>& arr)
{
    if(s>e) return;
    
    //Leaf node
    if(s==e){
        Stree[pos]=arr[s].ss;
        return;
    }

    Build(2*pos,s,(s+e)/2,arr);
    Build(2*pos+1,(s+e)/2+1,e,arr);
    Stree[pos] = Stree[2*pos]+Stree[2*pos+1];
}

ll query(ll x,ll y,ll l,ll r,ll pos)
{
    if(x>y) return 0;

    if(lazy[pos]!=0){
        if(l!=r){
            lazy[2*pos] += lazy[pos];
            lazy[2*pos+1] += lazy[pos];
        }
        Stree[pos] += lazy[pos]*(r-l+1);
        lazy[pos] = 0;
    }

    if(x<=l&&r<=y)
        return Stree[pos];

    if(y<l||x>r) return 0;

    ll temp1 = query(x,y,l,(l+r)/2,2*pos);
    ll temp2 = query(x,y,(l+r)/2+1,r,2*pos+1);
    return temp1+temp2;
}

void update(ll x,ll y,ll l,ll r,ll pos,ll val)
{
    if(x>y) return;
    if(lazy[pos]!=0){
        if(l!=r){
            lazy[2*pos] += lazy[pos];
            lazy[2*pos+1] += lazy[pos];
        }
        Stree[pos] += lazy[pos]*(r-l+1);
        lazy[pos] = 0;
    }

    if(x<=l&&r<=y){
        Stree[pos] += (r-l+1)*val;
        if(l!=r){
            lazy[2*pos] += val;
            lazy[2*pos+1] += val;
        }
        return;
    }

    if(y<l||x>r) return;

    update(x,y,l,(l+r)/2,2*pos,val);
    update(x,y,(l+r)/2+1,r,2*pos+1,val);
    Stree[pos] = Stree[2*pos]+Stree[2*pos+1];
}

int main()
{
    // fast
    ll t_c;t_c = 1;
    // cin>>t_c;
    for (ll ti = 0; ti < t_c; ++ti)
    {   
        ll n,d,a;cin>>n>>d>>a;
        vector<pair<ll,ll>> arr;
        arr.pb(mp(INT_MIN,INT_MIN));
        for(ll i=1;i<=n;++i){
            ll x,y;cin>>x>>y;
            arr.pb(mp(x,y));
        }
        sort(arr.begin(),arr.end());

        Build(1,1,n,arr);

        ll ans=0;
        for(ll i=1;i<=n;++i){
            ll curr=query(i,i,1,n,1);

            if(curr<=0) continue;
            if(curr%a==0){
                ans+=curr/a;
                ll upto=upper_bound(arr.begin(),arr.end(),mp(arr[i].ff+2*d,ll_MAX))-arr.begin();
                update(i,upto-1,1,n,1,-1*(curr/a)*a);
            }
            else{
                ans+=curr/a+1;
                ll upto=upper_bound(arr.begin(),arr.end(),mp(arr[i].ff+2*d,ll_MAX))-arr.begin();
                update(i,upto-1,1,n,1,-1*(curr/a+1)*a);
            }
        }
        cout<<ans;
    }
    return 0;
}   

Compiler output:
In file included from /usr/include/c++/14/bits/stl_algobase.h:71,
                 from /usr/include/c++/14/algorithm:60,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:51,
                 from a.cc:1:
/usr/include/c++/14/bits/predefined_ops.h: In instantiation of 'bool __gnu_cxx::__ops::_Val_less_iter::operator()(_Value&, _Iterator) const [with _Value = const std::pair<long long int, long int>; _Iterator = __gnu_cxx::__normal_iterator<std::pair<long long int, long long int>*, std::vector<std::pair<long long int, long long int> > >]':
/usr/include/c++/14/bits/stl_algo.h:1993:14:   required from '_ForwardIterator std::__upper_bound(_ForwardIterator, _ForwardIterator, const _Tp&, _Compare) [with _ForwardIterator = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Tp = pair<long long int, long int>; _Compare = __gnu_cxx::__ops::_Val_less_iter]'
 1993 |           if (__comp(__val, __middle))
      |               ~~~~~~^~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/stl_algo.h:2028:32:   required from '_FIter std::upper_bound(_FIter, _FIter, const _Tp&) [with _FIter = __gnu_cxx::__normal_iterator<pair<long long int, long long int>*, vector<pair<long long int, long long int> > >; _Tp = pair<long long int, long int>]'
 2028 |       return std::__upper_bound(__first, __last, __val,
      |              ~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
 2029 |                                 __gnu_cxx::__ops::__val_less_iter());
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
a.cc:112:36:   required from here
  112 |                 ll upto=upper_bound(arr.begin(),arr.end(),mp(arr[i].ff+2*d,ll_MAX))-arr.begin();
      |                         ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/predefined_ops.h:98:22: error: no match for 'operator<' (operand types are 'const std::pair<long long int, long int>' and 'std::pair<long long int, long long int>')
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:67:
/usr/include/c++/14/bits/stl_iterator.h:1241:5: note: candidate: 'template<class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator<(const __normal_iterator<_IteratorL, _Container>&, const __normal_iterator<_IteratorR, _Container>&)'
 1241 |     operator<(const __normal_iterator<_IteratorL, _Container>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1241:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const __gnu_cxx::__normal_iterator<_IteratorL, _Container>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1249:5: note: candidate: 'template<class _Iterator, class _Container> bool __gnu_cxx::operator<(const __normal_iterator<_Iterator, _Container>&, const __normal_iterator<_Iterator, _Container>&)'
 1249 |     operator<(const __normal_iterator<_Iterator, _Container>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1249:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const __gnu_cxx::__normal_iterator<_Iterator, _Container>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181:
/usr/include/c++/14/bits/regex.h:1143:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1143 |     operator<(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1143:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1224 |     operator<(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1224:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator<(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1317 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1317:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1391 |     operator<(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1391:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1485 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1485:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1560 |     operator<(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1560:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'std::pair<long long int, long long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator<(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1660 |     operator<(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1660:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::__cxx11::sub_match<_BiIter>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
In file included from /usr/include/c++/14/bits/stl_algobase.h:64:
/usr/include/c++/14/bits/stl_pair.h:1045:5: note: candidate: 'template<class _T1, class _T2> constexpr bool std::operator<(const pair<_T1, _T2>&, const pair<_T1, _T2>&)'
 1045 |     operator<(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_pair.h:1045:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   deduced conflicting types for parameter '_T2' ('long int' and 'long long int')
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_Iterator>&)'
  448 |     operator<(const reverse_iterator<_Iterator>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:448:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const reverse_iterator<_Iterator>&, const reverse_iterator<_IteratorR>&)'
  493 |     operator<(const reverse_iterator<_IteratorL>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:493:5: note:   template argument deduction/substitution failed:
/usr/include/c++/14/bits/predefined_ops.h:98:22: note:   'const std::pair<long long int, long int>' is not derived from 'const std::reverse_iterator<_Iterator>'
   98 |       { return __val < *__it; }
      |                ~~~~~~^~~~~~~
/usr/include/c++/14/bits/stl_iterator.h:1694:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator<(const move_iterator<_IteratorL>&,