#include <bits/stdc++.h>
#define NMAX 100000
using namespace std;
ifstream f("lupu.in"); ofstream g("lupu.out");
long long n, m, x, l, sol;
priority_queue <long long> pq;
pair <long long, long long> v[NMAX+1000];
inline bool mycmp(pair <long long, long long> a, pair <long long, long long> b)
{   return a.first > b.first; }
int main()
{   f >> n >> x >> l;
    for(long long a, b, i=1; i<=n; i++)
        {   f >> a >> b;
            if(a <= x)
                {   v[++m].first = (x - a) / l + 1;
                    v[m].second = b;
                }
        }
    n = m;
    sort(v+1, v+n+1, mycmp);
    long long i=1;
    while(i <= n)
    {   pq.push(v[i].second);
        while(i <= n && v[i].first == v[i+1].first) pq.push(v[i+1].second), i++;
        i++;
        for(long long j=1; j<=v[i-1].first-v[i].first; j++)
        {   long long val = pq.top();
            pq.pop();
            sol += val;
        }
    }
    g << sol << '\n';
    g.close(); return 0;
}