#include <cstdio>
#include <algorithm>
#include <set>
#include <climits>
#include <cctype>
using namespace std;
const int INF = INT_MAX;
const int NMAX = 100000;
char buffer[1 << 17];
int sz = (1 << 17) , crs = (1 << 17);
void get_int(int &n)
{
    for( ; crs < sz && !isdigit(buffer[crs]) ; crs ++);
    if(crs == sz)
    {
        fread(buffer , sz , 1 , stdin);
        for(crs = 0 ; crs < sz && !isdigit(buffer[crs]) ; crs ++);
    }
    n = 0;
    for( ; crs < sz && isdigit(buffer[crs]) ; crs ++)
        n = n * 10 + buffer[crs] - '0';
    if(crs == sz)
    {
        fread(buffer , sz , 1 , stdin);
        for(crs = 0 ; crs < sz && isdigit(buffer[crs]) ; crs ++)
            n = n * 10 + buffer[crs] - '0';
    }
}
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)
{
    if(a.y == b.y)
        return a.x > b.x;
    return a.y > b.y;
}
int main()
{
    freopen("lupu.in", "r", stdin);
    freopen("lupu.out", "w", stdout);
    int n, r, l, i, x, y, cnt, maxim;
    long long sum = 0;
    get_int(n);
    get_int(r);
    get_int(l);
    set <int> s;
    set <int>::iterator it;
    for(i = 1 ; i <= n ; ++ i)
    {
        get_int(x);
        get_int(y);
        v[i]= {(r - x) / l + 1, y};
        s.insert(i);
    }
    sort(v + 1, v + n + 1, cmp);
    s.insert(INF);
    for(i = 1 ; i <= n ; ++ i)
    {
        if(v[i].x > n)
        {
            sum += v[i].y;
            continue;
        }
        it = lower_bound(s.begin(), s.end(), v[i].x);
        if(it != s.begin() && (*it) != v[i].x)
            it --;
        if(*it <= v[i].x)
        {
            sum += v[i].y;
            s.erase(it);
        }
    }
    printf("%lld\n", sum);
    return 0;
}