#include<fstream>
#include<set>
#define a first
#define b second
using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
int n,x,l,in,r;
pair<int,int >v[100005];
int main()
{
    fin>>n>>x>>l;
    for(int i=1;i<=n;i++)
        fin>>v[i].a>>v[i].b;
    while(1)
    {
        int p=1,ma=-1;
        for(int i=1;i<=n;i++)
            if(v[i].a-in<=x&&v[i].a-in+l>x&&v[i].b>ma)
            {
                p=0;
                ma=v[i].b;
            }
        if(p==1)
            break;
        else
            r+=ma;
        in-=l;
    }
    fout<<r;
}