#include <fstream>
#include<queue>
#include<algorithm>
using namespace std;

ifstream cin("lupu.in");
ofstream cout("lupu.out");

priority_queue<int> s;
pair<int,int> v[100010];

signed main()
{
    int n,x,l,i,d,a,rasp=0,j;
    cin>>n>>x>>l;
    for(i=1;i<=n;i++)
        cin>>v[i].first>>v[i].second;
    sort(v+1,v+n+1);
    i=1;
    for(j=0;j<=x;j+=l){
        while(i<=n && v[i].first<=j){
            s.push(v[i].second);i++;
        }
        if(!s.empty())
            rasp+=s.top();s.pop();
    }
    cout<<rasp;
    return 0;
}