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 PYTHON3):

Solution:
from bisect import bisect_right
n,d,a=map(int,input().split())
xh=[list(map(int,input().split()))for _ in range(n)]
xh.sort()
x=[]
h=[]
for xx,hh in xh:
  x.append(xx)
  h.append(hh)

not_imos=[0]*(n+1)
atk_n=0
ans=0
for i in range(n):
  atk_n-=not_imos[i]
  h[i]-=atk_n*a
  if h[i]<0:h[i]=0
  atk_i=0--h[i]//a
  ans+=atk_i
  atk_n+=atk_i
  not_imos[bisect_right(x,x[i]+d*2)]+=atk_i
print(ans)