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

#define NMAX 100005
using namespace std;

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

struct chestie
{
    int grupa, gr;
} v[NMAX];

inline bool cmp1(chestie a, chestie b)
{
    if(a.grupa == b.grupa)
        return (a.gr > b.gr);
    return (a.grupa < b.grupa);
}

inline bool cmp2(chestie a, chestie b){
    return a.gr < b.gr;
}

vector<chestie> taken;

int main()
{
    int n, hm, u;
    fin >> n >> hm >> u;

    for(int i = 1; i <= n; ++i)
    {
        int h, g;
        fin >> h >> g;

        v[i].grupa = (hm - h) / u + 1;
        v[i].gr = g;
    }

    sort(v + 1, v + n + 1, cmp1);

    taken.push_back(v[1]);
    int i = 2;
    int grup = 2;
    while(grup <= v[n].grupa)
    {
        while(v[i].grupa == grup - 1)
            ++i;
        taken.push_back(v[i]);
        if(i == n)
            break;
        ++i;
        while(v[i].grupa == grup){
            sort(taken.begin(), taken.end(), cmp2);
            if(taken[0].gr < v[i].gr)
                taken[0] = v[i];
            ++i;
        }
    }

    long long s = 0;
    for(int i = 0; i < taken.size(); ++i)
        s += taken[i].gr;
    fout << s << '\n';
    return 0;
}