#include <bits/stdc++.h>

using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
#define int long long
int n, pozMax, L, maxim = 0;
unordered_map<int, vector<int>> tin;

signed main()
{
    fin >> n >> pozMax >> L;
    for(int i=1; i<=n; i++) {
        int poz, val; fin >> poz >> val;
        int cntTure = (pozMax - poz) / L + 1; ///cate ture am oaia
        tin[cntTure].push_back(val);
        maxim = max(maxim, cntTure);
    }
    int sum = 0;
    priority_queue<int> pq;
    for(int i=maxim; i>=1; i--) {
        for(int j : tin[i]) pq.push(j);
        sum += pq.top(); pq.pop(); ///aleg oaia din tura i
    }
    fout << sum;

    return 0;
}