#include<fstream>
#include<set>
#include<algorithm>
#include<vector>
#define a first
#define b second
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
int n,x,l,in,b[100005],ma,j=1;
long long r;
pair<int,int >v[100005];
typedef pair<int,int >pii;
int cmp(pii A,pii B)
{
    if(A.a<B.a)
        return 1;
    return 0;
}
int nex(int g)
{
    if(g%l==0)
        return g;
    return g/l*l+l;
}
multiset<int,greater<int> >z;
int main()
{
    fin>>n>>x>>l;
    for(int i=1;i<=n;i++)
        fin>>v[i].a>>v[i].b;
    sort(v+1,v+n+1,cmp);
    for(int i=0;i<=x;i+=l)
    {
        for(;j<=n&&v[j].a<=i;j++)
            z.insert(v[j].b);
        r+=*z.begin();
        if(*z.begin()==0&&l!=0)
            i=nex(j);
        z.erase(z.begin());
    }
    fout<<r;
}