#include<cstdio>
#include<vector>
#include<set>

using namespace std;

multiset<int> h,v[100006];
long long n,k,l,i,mx,d,PUF,s;

int main()
{
    freopen("lupu.in","r",stdin);
    freopen("lupu.out","w",stdout);
    scanf("%lld%lld%lld",&n,&k,&l);
    mx=0;
    s=0;
    for(i=1;i<=n;i++)
    {
        scanf("%lld%lld",&d,&PUF);
        v[((k-d)/l)+1].insert(PUF);
        if((k-d)/l>=mx)
        {
            mx=(k-d)/l;
            mx++;
        }
    }
    multiset<int> ::iterator it,it2;
    for(i=mx;i>=1;i--)
    {
        for(it=v[i].begin();it!=v[i].end();it++)
        {
            h.insert((*it));
        }
        it2=h.end();
        it2--;
        s+=*it2;
        h.erase(it2);
    }
    printf("%lld\n",s);
}