#include<cstdio>
#include<algorithm>
#include<queue>

using namespace std;

priority_queue<int> hx;

const int maxN=100005;
pair<int,int> a[maxN];
int n,h,u,s;

bool comp(pair<int,int> v1, pair<int,int> v2)
{
	if(v1.first<v2.first)
		return true;
	else return false;
}
void read()
{
	int i,j;
	freopen("gutui.in","r",stdin);
	freopen("gutui.out","w",stdout);
	scanf("%d%d%d",&n,&h,&u);
	for(i=1;i<=n;++i)
		scanf("%d%d",&a[i].first,&a[i].second);
}

void work()
{
	int i,da,hh;
	sort(a+1,a+n+1,comp);
	hh=h;
	while(hh-u>=a[1].first)
		hh-=u;
	i=1; da=1;
	while(da)
	{
		if(a[i].first<=hh && i<=n)
		{
			hx.push(a[i].second);
			++i;
		}
		else
		{
			if(!hx.empty())
			{
				s+=hx.top();
				hx.pop();
			}
			hh+=u;
			if(hh>h)
				da=0;
		}
	}
}

int main()
{
	read();
	work();
	printf("%d\n",s);
	return 0;
}