#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;
ifstream f("lupu.in");
ofstream g("lupu.out");
priority_queue<int> ST;
pair <int,int> a[100010];
int n,x,k,d,i;
long long sol;
int main()
{   f>>n>>x>>k;
    for(i=1;i<=n;++i) f>>a[i].first>>a[i].second;
    sort(a+1,a+n+1);
    for(d=0,i=1;d<=x;d+=k)
    {   while(i<=n && a[i].first<=d) ST.push(a[i++].second);
        if(!ST.empty()) {sol+=ST.top(); ST.pop();}
    }
    g<<sol;
}