#include <cstdio>
#include <set>
#include <algorithm>
using namespace std;

struct oita {
    int lana,strat;
};
oita oaie[100005];
int n,i,k,l,distanta,lana,nr;
long long totalLana;

struct comp {
    inline bool operator()(const int &a,const int &b) {
        return (a>b);
    }
};
multiset <int,comp> heap;

bool cmp(oita a,oita b) {
    return (a.strat>b.strat);
}

int main() {
    freopen("lupu.in","r",stdin);
    freopen("lupu.out","w",stdout);

    scanf("%d %d %d",&n,&l,&k);
    for (i=1;i<=n;i++) {
        scanf("%d %d",&distanta,&lana);
        if(l>=distanta){
            nr++;
            oaie[nr].lana=lana;
            oaie[nr].strat = (l-distanta)/k;
        }
    }
    n=nr;
    sort(oaie+1,oaie+n+1,cmp);
    heap.insert(oaie[1].lana);
    for (i=2;i<=n;i++) {
        if (oaie[i].strat == oaie[i-1].strat)
            heap.insert(oaie[i].lana);
        else {
            int x = oaie[i-1].strat - oaie[i].strat;
            for (int j=1;j<=x;j++) {
                if (heap.empty()) break;
                totalLana += (long long)*heap.begin();
                heap.erase(heap.begin());
            }
            heap.insert(oaie[i].lana);
        }
    }
    if (oaie[n].strat == 0 && !heap.empty()) totalLana += (long long)*heap.begin();
    printf("%lld\n",totalLana);
    return 0;
}