#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>

using namespace std;

ifstream fin("lupu.in");
ofstream fout("lupu.out");

vector< pair<int,int> > values;
int main()
{
    int n,x,l;
    fin >> n >> x >>l;
    for (int i=0;i<n;i++)
    {
        int a,b;
        fin >> a >> b;
        values.push_back(make_pair(a,b));
    }
    sort(values.rbegin(),values.rend());

    int lu = x;
    int ll = x-l+1;
    int maxim=0;
    int total=0;
    for (int i=0;i<n;i++)
    {
        if (ll<=values[i].first&&values[i].first<=lu)
        {
            maxim  = max(values[i].second,maxim);
        }
        else
        {
            total += maxim;
            maxim = values[i].second;
           // cout << maxim <<endl;
            lu = values[i].first + (l - values[i].first%l)%l;// round up
            ll = lu - l +1;
           // cout << ll<<" "<<lu<<endl;
        }
    }
    total+=maxim;
    fout << total;
}