#include <bits/stdc++.h>
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");
const int N = 1e5+5;
vector< pair<int,int> > v;
int main()
{
    int n,x,l;
    long long s = 0;
    in >> n >> x >> l;
    for (int i = 1; i<=n; i++)
    {
        int a,d;
        in >> d >> a;
        if (d<=x)
            v.push_back({(x-d)/l+1,-a});
    }
    sort(v.begin(),v.end());
    reverse(v.begin(),v.end());
    for (int pas = 1; pas<=n; pas++)
    {
        while (v.back().first>pas)
            v.pop_back();
        if (!v.empty())
            s-=v.back().second;
        else
            break;
        while (v.back().first == pas)
            v.pop_back();
    }
    out << s;
}