#include<fstream>
#include<algorithm>
#include<queue>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
priority_queue<int>heap;
pair<int,int>v[100005];
int main()
{
    int i,n,x,l,j;
    long long sol=0;
    f>>n>>x>>l;
    for(i=1;i<=n;i++)
      f>>v[i].first>>v[i].second;
    sort(v+1,v+n+1);
    for(j=0,i=1;j<=x;j=j+l)
    {
        while(i<=n&&v[i].first<=j)
          heap.push(v[i++].second);
        if(!heap.empty())
        {
            sol=sol+heap.top();
            heap.pop();
        }
    }
    g<<sol;
    return 0;
}