#include <bits/stdc++.h>

using namespace std;
ifstream fin("lupu.in");
ofstream fout("lupu.out");
priority_queue<int> q;
pair<int,int> a[100005];
int n,x,l,ans;
int main()
{   fin>>n>>x>>l;
    for(int i=1;i<=n;i++) fin>>a[i].first>>a[i].second;
    sort(a+1,a+n+1);
    int j=1;
    for(int i=x/l;i>=0;i--){
        while(j<=n&&a[j].first+i*l<=x){q.push(a[j].second);j++;}
        if(!q.empty()) {ans+=q.top();q.pop();}
    }
    fout<<ans;
    return 0;
}