#include<bits/stdc++.h>
using namespace std;
ifstream in("lupu.in");
ofstream out("lupu.out");
int n,x,l,s;
priority_queue <int> q;
struct abc{
    int x,y;
}a[100005];
int comp(abc a, abc b) {
    return a.x<b.x;
}
int main()
{in>>n>>x>>l;
for(int i=1;i<=n;i++)
    in>>a[i].x>>a[i].y,a[i].x=(x-a[i].x)/l;
sort(a+1,a+n+1,comp);
int k=a[n].x;
while(k>=0)
    {while(n && a[n].x>=k)
        q.push(a[n--].y);
    //cout<<q.top()<<' ';
    if(!q.empty())
        s+=q.top(),q.pop();
    k--;
    }
out<<s<<'\n';
return 0;
}