#include <cstdio>
#include <queue>
#include <vector>

using namespace std;
const int MAX=1000000;

priority_queue<int> pq;
vector<int> v[MAX + 1];
int d, a, i, j, t, n, x, l, maxx;
long long s=0;

int main()
{
    freopen("lupu.in", "r", stdin);
    freopen("lupu.out", "w", stdout);

    scanf("%d%d%d", &n, &x, &l);

    for(i = 1; i <= n; i ++)
    {
        scanf("%d%d", &d, &a);
        t = 0;
        if(d > x)
         t = 0;
        else
            t = 1 + (x - d) / l;
        v[t].push_back(a);
        if (t > maxx) maxx = t;
    }

    for(i = maxx; i > 0; i --)
    {
        if(!v[i].empty())
        {
            for(j = 0; j < v[i].size(); j ++)
            {
                pq.push(v[i][j]);
            }
        }
        if(!pq.empty())
        {
            s = s + pq.top();
            pq.pop();
        }
    }

    printf("%lld\n",s);
    return 0;
}