#include<fstream>
#include<queue>
#include<algorithm>
using namespace std;ifstream f("lupu.in");ofstream g("lupu.out");priority_queue<int> pq;pair <int,int> a[100001];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) pq.push(a[i++].second);if(!pq.empty()) {sol+=pq.top(); pq.pop();}}g<<sol;}