#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;
int N, X, L, T = 0;
int REZ = 0;
const int NMAX = 100009;
int O[NMAX];
int lana[NMAX];
int B[NMAX];
int ln2[NMAX];

void citire()
{
	int timp, ln;
	scanf("%d%d%d",&N,&X,&L);
	for(int i = 1; i <= N ; i++)
	{
		scanf("%d%d", &timp, &ln);
		timp = 1 + (X - timp) / L;
		if(timp > T)
			T = timp;
		O[i] = timp;
		lana[i] = ln;
	}
}

void merge_sort(int l, int r)
{
    int m = (l + r) >> 1, i, j, k;
    if (l == r) return;
    merge_sort(l, m);
    merge_sort(m + 1, r);
    for (i=l, j=m+1, k=l; i<=m || j<=r; )
        if (j > r || (i <= m && O[i] < O[j]))
            B[k] = O[i], ln2[k++] = lana[i++];
        else
            B[k] = O[j], ln2[k++] = lana[j++];
    for (k = l; k <= r; k++) O[k] = B[k], lana[k] = ln2[k];
}

struct cmp
{
	bool operator()(const int &a, const int &b)const
	{
		return lana[a] < lana[b];
	}
};

priority_queue <int, vector<int>, cmp> Q;

void rezolva()
{
	int nr = N;
	for(int i = T ; i ; --i)
	{
		int j = nr;
		while(O[j] == O[nr])
		{
			Q.push(j);
			j--;
		}
		while(1)
		{
			if(O[Q.top()]  >= O[nr])
				break;
			Q.pop();
		}
		REZ += lana[Q.top()];
		Q.pop();
		nr = j;
	}
}

int main()
{
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	citire();
	merge_sort(1, N);
	rezolva();
	printf("%d",REZ);

	return 0;
}