#include<bits/stdc++.h>
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");

vector<pair<int, int>>v;
priority_queue<int>q;

int main()
{
    int n,x,l,i,a,b;
    fin>>n>>x>>l;
    for(i=1;i<=n;i++)
    {
        fin>>a>>b;
        v.push_back(make_pair(a, b));
    }
    sort(v.begin(), v.end());
    long long sum=0;
    int ind=0;
    for(i=0;i<=x;i+=l)
    {
        while(ind<n && v[ind].first<=i)
        {
            q.push(v[ind].second);
            ind++;
        }
        if(q.size()!=0)
        {
            sum+=q.top();
            q.pop();
        }
    }
    fout<<sum;
    return 0;
}