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:
n,d,a=map(int,input().split())
arr=[list(map(int,input().split())) for _ in range(n)]
arr=sorted(arr,key=lambda x:x[0])
lim=[0]*n
pos=0
for i in range(n):
  while pos!=n-1:
    if arr[i][0]+2*d>=arr[pos+1][0]:
      pos+=1
    else:
      break
  lim[i]=pos
ans=0
damage=[0]*n
acum=0
pos=0
for i in range(n):
  while i>lim[pos]:
    acum-=damage[pos]
    pos+=1
    if pos==n:
      break
  ans+=max(0,(arr[i][1]-acum+(a-1))//a)
  damage[i]=a*max(0,(arr[i][1]-acum+(a-1))//a)
  acum+=damage[i]
print(ans)