#include <bits/stdc++.h>
#define ll long long
#define int ll
#define ld long double
#define pii pair<int, int>
#define tpl tuple<int, int, int>
#define piv pair<int, vector<int>>
#define eb emplace_back
#define oo INT_MAX / 2
#define OO LLONG_MAX / 2
using namespace std;

const string fn("lupu");

ifstream in(fn + ".in");
ofstream out(fn + ".out");

#define cin in
#define cout out

class cmp{
    public:
        bool operator()(pii a,pii b)
        {
            if(a.first<b.first)
                return 1;
            if(a.first==b.first and a.second<b.second)
                return 1;
            return 0;
        }
};

int N,X,L;
map<int,set<int>> M;
set<int> s;

void solve()
{
    cin>>N>>X>>L;

    for(int i=1;i<=N;i++)
    {
        int d,a;
        cin>>d>>a;
        int r=(X-d)/L;
        M[r].insert(-a);
        s.insert(r);

        ///cout<<a<<' '<<d<<' '<<r<<'\n';
    }

    int timer=0,ans=0;

    for(auto x: M)
    {
        auto it=x.second.begin();
        while(timer<=x.first and it!=x.second.end())
        {
            ans+=-*it;
            it++;
            ///cout<<x.first<<' '<<timer<<'\n';
            timer++;
        }
    }
    cout<<ans;
}

signed main()
{
    int q = 1;

    /// cin >> q;
    while (q--)
        solve();
    return 0;
}