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

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

#define int long long

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

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