#include <cstdio>
#include <algorithm>
#include <queue>
#define MAX 100100
using namespace std;
struct lup{
    int dist,lana;
};
lup q[MAX];
bool cmp(lup a,lup b)
{
    return a.dist<b.dist;
}
priority_queue <int> heap;
int main()
{
    int n,x,l;
    int i,w;
    long long sol=0;
    freopen("lupu.in","r",stdin);
    freopen("lupu.out","w",stdout);
    scanf("%d%d%d",&n,&x,&l);
    for(i=1;i<=n;++i)
        scanf("%d%d",&q[i].dist,&q[i].lana);
    sort(q+1,q+n+1,cmp);
    for(i=1,w=0;i<=n and q[i].dist<=x;w+=l){
        while(i<=n and q[i].dist<=w)
            heap.push(q[i].lana),++i;
        if(heap.size())
            sol+=heap.top(),heap.pop();
    }
    printf("%lld\n",sol);
    return 0;
}