#include<algorithm>
#include<cstdio>

using namespace std;

const int NMAX = 100000+5;

struct Gutuie
{
    int height,weight,fruits;

    void Set(int h,int w,int f)
    {
        height=h;
        weight=w;
        fruits=f;
    }

    bool operator()(Gutuie A,Gutuie B)
    {
        if(A.fruits==B.fruits) return A.weight>B.weight;
        return A.fruits<B.fruits;
    }
};

int N,H,U,NrG;
long long WeG;
Gutuie V[NMAX];

int main()
{
    int i,h,w,f;

    freopen("gutui.in","r",stdin);
    freopen("gutui.out","w",stdout);

    scanf("%d%d%d",&N,&H,&U);

    for(i=1; i<=N; i++)
    {
        scanf("%d%d",&h,&w);
        if(h>H) f=-1;
        else f=(H-h)/U;
        V[i].Set(h,w,f);
    }

    sort(V+1,V+N+1,Gutuie());

    for(i=1; i<=N; i++)
        if(V[i].fruits>=NrG)
        {
            NrG++;
            WeG+=1LL*V[i].weight;
        }

    printf("%lld\n",WeG);

    return 0;
}