#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin("lupu.in");
ofstream g("lupu.out");

int n, x, l;
struct lup{
            int d, b;}v[100005], v1[100005];

bool cmp(lup a, lup b)
{
    return a.b > b.b;
}


int main()
{
    int a, b, s=0, l0, i, cl;
    fin>>n>>x>>l;
    l0=l;
    cl=0;
    for(int i=1;i<=n;i++)
    {
        fin>>v[i].d>>v[i].b;
        v1[i].d=v[i].d;
        v1[i].b=v[i].b;
    }
    sort(v1 + 1, v1 + n + 1, cmp);
    
    int k=1,  j;
    while(k!=0)
    {
        k=0;
        int max=0;
        for(i=1;i<=n;i++)
        {
	if(v[i].d<=x)
            if(v[i].d+l>x && v[i].b>max)
            {
                j=i;
                max=v[i].b;
            }
        }
        s+=max;
        
        
        for(i=1;i<=n;i++)
        if(v[i].d+l>x) 
                {
                    v[i].b=-1;
                    v[i].d=-1;
                }
                
        for(i=1;i<=n && k!=1;i++)
            {   
                if(v[i].b!=-1) k=1;

            }
        l+=l0;
    }
    k=1;
    int s1=0; 
    for(i=1;i<=n&&k!=0;i++)
    {
        if(v1[i].d<=x)
            if(v1[i].d+cl<=x)
            {
                s1+=v1[i].b;
                cl+=l0;
            }
            else {
                k=0;
            }
    }
    if(s1>s) g<<s1;
    else g<<s;
    
    return 0;
}