#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

int n,x,l;
priority_queue<pii> pq;

void solve()
{
    cin>>n>>x>>l;

    for(int i=1;i<=n;i++)
    {
        int d,a;
        cin>>d>>a;

        int timer=0;

        int r=x-d;
        timer=r/l;

        pq.emplace(a,timer);
    }

    int timer=0,ans=0;

    while(!pq.empty())
    {
        int w,t;
        tie(w,t)=pq.top();
        pq.pop();

        if(timer<=t)
        {
            ans+=w;
            timer++;
        }
    }

    cout<<ans;
}

signed main()
{
    int q = 1;

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