#include <iostream>
#include <fstream>
#include <queue>

using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");

int n, x, l;

priority_queue<pair<int,int>> a;

int main()
{
    fin >> n >> x >> l;
    for(int i = 0; i < n; i++)
    {
        int a1, a2;
        fin >> a1 >> a2;
        a.push({a2, a1});
    }
    int p = 0;
    long long sum = 0;
    while(!a.empty())
    {
        pair<int,int> crt = a.top();
        a.pop();
        int dis = crt.second + (l*p);
        if(dis > x)
            continue;
        int adaug = crt.first;
        sum += (1LL*adaug);
        p++;
    }
    fout << sum;
    return 0;
}