#include <bits/stdc++.h>

using namespace std;

struct oi
{
    int d,l;
} v[100001];
bool cmp(oi a, oi b)
{
    return a.d<b.d;
}
priority_queue<int> q;

int main()
{
    ifstream cin("lupu.in");
    ofstream cout("lupu.out");
    int n,x,l,i,j,p=0;
    long long s=0;
    cin>>n>>x>>l;
    for(i=0;i<n;i++)
       cin>>v[i].d>>v[i].l;
    sort(v,v+n,cmp);
    for(i=0; i<=x; i+=l)
    {
        while(p < n && v[p].d <= i)
            q.push(v[p].l),p++;
        if(q.size()!=0)
            s+=q.top(),q.pop();
    }
    cout<<s;
    return 0;
}