Problem: Silver Fox is fighting with N monsters.

The monsters are standing in a row, and we can assume them to be standing on a number line. The i-th monster, standing at the coordinate X_i, has the health of H_i.

Silver Fox can use bombs to attack the monsters. Using a bomb at the coordinate x decreases the healths of all monsters between the coordinates x-D and x+D (inclusive) by A. There is no way other than bombs to decrease the monster's health.

Silver Fox wins when all the monsters' healths become 0 or below.

Find the minimum number of bombs needed to win.

Constraints

* 1 \leq N \leq 2 \times 10^5
* 0 \leq D \leq 10^9
* 1 \leq A \leq 10^9
* 0 \leq X_i \leq 10^9
* 1 \leq H_i \leq 10^9
* X_i are distinct.
* All values in input are integers.

Input

Input is given from Standard Input in the following format:


N D A
X_1 H_1
:
X_N H_N


Output

Print the minimum number of bombs needed to win.

Examples

Input

3 3 2
1 2
5 4
9 2


Output

2


Input

9 4 1
1 5
2 4
3 3
4 2
5 1
6 2
7 3
8 4
9 5


Output

5


Input

3 0 1
300000000 1000000000
100000000 1000000000
200000000 1000000000


Output

3000000000

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
using namespace std;
const int N=2e5+50;
pair<long long,long long> m[N],b[N];
long long cnt;
int main()
{
	long long n,d,a;
	cin>>n>>d>>a;
	for (int i=0;i<n;i++)
		cin>>m[i].first>>m[i].second;
	sort(m,m+n);
	long long ans=0,cnt=0,l=1,sum=0;
	for (int i=0;i<n;i++)
	{
		while (l<=cnt)
		{
			if (b[l].first+d>=m[i].first)
				break;
			sum-=b[l].second;
			l++;
		}
		if (m[i].second<=sum)
			continue;
		m[i].second-=sum;
        long long num=(m[i].second+a-1)/a,v=num*a;
        b[++cnt]= make_pair(m[i].first+d,v);
        sum+=v;
        ans+=num;
	}
	cout<<ans;
	return 0;
}