#include <cstdio>
#include <algorithm>
using namespace std;
const int NMAX = 100000;
struct lupu
{
    int x, y;
    lupu(int tx = 0, int ty = 0): x(tx), y(ty) {}
};
lupu v[NMAX + 5];
int cmp(lupu a, lupu b)
{
    return a.y > b.y;
}
int aib[NMAX + 5], n;
void update(int poz)
{
    for(int i = poz ; i <= n ; i += (i & (-i)))
        aib[poz] ++;
}
int query(int poz)
{
    int cnt = 0;
    for(int i = poz ; i > 0 ; i -= (i & (-i)))
        cnt += aib[poz];
    return cnt;
}
int main()
{
    freopen("lupu.in", "r", stdin);
    freopen("lupu.out", "w", stdout);
    int r, l, i, x, y, s, cnt;
    scanf("%d%d%d", &n, &r, &l);
    for(i = 1 ; i <= n ; i ++)
    {
        scanf("%d%d", &x, &y);
        v[i]= {(r - x) / l + 1, y};
    }
    sort(v + 1, v + n + 1, cmp);
    s = 0;
    for(i = 1 ; i <= n ; i ++)
    {
        cnt = query(v[i].x);
        if(cnt < v[i].x)
        {
            s += v[i].y;
            update(v[i].x);
        }
    }
    printf("%d\n", s);
    return 0;
}