//#pragma GCC optimize("O3, Ofast, unroll-loops")
#include <bits/stdc++.h>
using namespace std;

struct Cows
{
    int d, a;
}v[100005];

bool cmp(Cows x, Cows y)
{
    if(x.a==y.a)
        return x.d>y.d;
    return x.a>y.a;
}

int main()
{
    ifstream cin("lupu.in");
    ofstream cout("lupu.out");
    int n, x, l, nr=0, sum=0;
    cin>>n>>x>>l;
    for(int i=1; i<=n; i++)
    {
        cin>>v[i].d>>v[i].a;
    }
    sort(v+1, v+n+1, cmp);
    for(int i=1; i<=n; i++)
    {
        if(v[i].d+nr<=x)
        {
            nr+=l;
            sum+=v[i].a;
        }
    }
    cout<<sum;
    return 0;
}