#include <bits/stdc++.h>
using namespace std;
ifstream f ("lupu.in");
ofstream g ("lupu.out");
priority_queue <int> usu;
pair <int,int> v[100003];
int n,x,k,d,i;
long long ans;
int main()
{
    f>>n>>x>>k;
    for(i=1;i<=n;++i) f>>v[i].first>>v[i].second;
    sort(v+1,v+n+1);
    for(d=0,i=1;d<=x;d+=k)
    {
        while(i<=n&&v[i].first<=d) usu.push(v[i++].second);
        if(!usu.empty())
        {
            ans+=usu.top();
            usu.pop();
        }
    }
    g<<ans;
    return 0;
}