#include <algorithm>
#include <fstream>
#include <queue>
#define NMAX 100100
#define FOR(i,a,b) for(int i = a; i <= b; i++)
#define FORk(i,a,b,k) for(int i = a; i <= b; i+=k)
using namespace std;

pair<int, int> oi[NMAX];
priority_queue<int> q;


ifstream fin("lupu.in");
ofstream fout("lupu.out");
int N,L,D;

int main()
{
    int sol = 0;
    fin>>N>>D>>L;
    FOR(i,1,N)
        fin>>oi[i].first>>oi[i].second;
    sort(oi+1, oi+N+1);

    int i = 1;
    FORk(d,0,D,L)
    {
        while(i <= N && oi[i].first <= d)
            q.push(oi[i++].second);
        if(!q.empty())
        {
            sol += q.top();
            q.pop();
        }
    }

    fout << sol << '\n';

    return 0;
}