#include <bits/stdc++.h>

using namespace std;
const int mx=100001;
typedef long long ll;

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

struct oi
{
    ll lana,dist;
}v[mx];
priority_queue<ll> q;
int n,x,l;
ll rasp;

bool compara(oi vs,oi vd)
{
    return vs.dist<vd.dist;
}


void read()
{
    fin>>n>>x>>l;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i].dist>>v[i].lana;
    }
    sort(v+1,v+1+n,compara);
    int nr=(x-v[1].dist)/l;
    int j=1;
    for(int i=nr;i>=0;i--)
    {
        while(j<=n and v[j].dist+l*i<=x)
        {
            q.push(v[j].lana);
            j++;
        }
        rasp+=q.top();
        q.pop();
    }
    fout<<rasp;
}

int main()
{
    read();
    return 0;
}