#include <bits/stdc++.h>

using namespace std;
ifstream r("lupu.in");
ofstream w("lupu.out");
vector<pair<int, int>>v;
priority_queue<int>q;
int main()
{
    int n, x, l;
    r>>n>>x>>l;
    for(int i=0;i<n;i++){
        int a, b;
        r>>a>>b;
        v.push_back(make_pair(a, b));
    }
    sort(v.begin(), v.end());
    long long sum=0;
    int ind=0;
    for(int i=0;i<=x;i+=l){
        while(ind<n && v[ind].first<=i){
            q.push(v[ind].second);
            ind++;
        }
        if(q.size()!=0){
            sum+=q.top();
            q.pop();
        }
    }
    w<<sum;
    return 0;
}