#include <stdio.h>
#include <algorithm>
#define mx 100010

using namespace std;

struct oaie
{
	long long t, l;
} oi[mx];
long long n, x, l, maxim;
long hp[mx];

inline bool cmp(const oaie &a, const oaie &b)
{
	return (a.t<b.t);
}

void heapup(long x)
{
	if (hp[x] > hp[x / 2] && x > 1)
	{
		swap(hp[x],hp[x / 2]);
		if (x > 1)
			heapup(x / 2);
	}
}

void heapdown(long x)
{
	int maxim = 0;
	if (hp[0] >= (x << 1))
		maxim = x << 1;
	if (hp[0] > (x << 1) && hp[x << 1] < hp[(x << 1) + 1])
		maxim = (x << 1) + 1;
	if (hp[x] < hp[maxim])
	{
		swap(hp[x],hp[maxim]);
		heapdown(maxim);
	}
}

int main()
{
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%ld %ld %ld", &n, &x, &l);
	for (int i = 1; i <= n; i++)
		scanf("%ld %ld", &oi[i].t, &oi[i].l);
	sort(oi+1,oi+1+n,cmp);
	int ac = x % l;
	for (int i = 1; i <= n; i++)
	{
		if (oi[i].t > ac)
		{
			ac += l;
			maxim += (long long) hp[1];
			hp[1] = oi[i].l;
			heapdown(1);
		}
		else
		{
			hp[0]++;
			hp[hp[0]] = oi[i].l;
			heapup(hp[0]);
		}
	}
	maxim += (long long) hp[1];
	printf("%ld\n", maxim);
	fclose(stdin);
	fclose(stdout);
	return 0;
}