#include <bits/stdc++.h>
#define DMAX 100100
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
priority_queue<int> H;
struct oaie{int dist,lana,inter;};
oaie a[DMAX];
int n,distmax,dep,rest;
bool compar(oaie x,oaie y)
{
    return x.inter<y.inter;
}
int main()
{int i;
    fin>>n>>distmax>>dep;
    rest=distmax%dep;
    for(i=1;i<=n;i++)
        {fin>>a[i].dist>>a[i].lana;
        a[i].inter=a[i].dist/dep+1;
        if(!(a[i].dist%dep))
            a[i].inter--;

        }

    sort(a+1,a+n+1,compar);
    int nrmax=0;
    int nrint=0;
    int c1=1;
    while(nrint<=distmax/dep)
    {
        while(c1<=n&&a[c1].inter==nrint)
            H.push(a[c1].lana),c1++;
        nrmax+=H.top();
        H.pop();
        nrint++;
    }
    fout<<nrmax;
}