#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream fi("lupu.in");
ofstream fo("lupu.out");
struct oaie{int d,c;} v[100002];
int n,x,l;
bool cmp(oaie x,oaie y) {return x.c<y.c;}
int main(){
    fi>>n>>x>>l;
    for (int i=1;i<=n;i++)
        fi>>v[i].d>>v[i].c;
    sort(v+1,v+n+1,cmp);
    int s=0,i=n;
    while (x>=0&&i>0) {
        while (v[i].d>x&&i>0)
            i--;
        if (i>0)
            s=s+v[i].c;
        x=x-l;
        i--;
    }
    fo<<s;
    return 0;
}