#include <fstream>
#include <queue>
#include <algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
const int nmax = 100005;
struct oaie{
    long long lana, timp;
    bool operator < (const oaie o){
        return timp < o.timp;
    }
};
oaie oi[nmax];
priority_queue<long long> q;
long long sol;
long long n, l, x;
int main(){
    f >> n >> x >> l;
    for(int i = 1; i <= n; i++){
        int d;
        f >> d >> oi[i].lana;
        oi[i].timp = (x - d) / l;
    }
    sort(oi + 1, oi + n + 1);
    int p = n;
    int t = oi[n].timp;
    while(t >= 0){
        while(p > 0 && oi[p].timp >= t){
            q.push(oi[p].lana);
            p--;
        }
        sol += q.top();
        q.pop();
        t--;
    }
    g << sol;
}