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:
def nibun_right(a, x, lo=0, hi=None):
 if lo < 0:
  raise ValueError('lo must be non-negative')
 if hi is None:
  hi = len(a)
 while lo < hi:
  mid = (lo+hi)//2
  if x < a[mid][0]: hi = mid
  else: lo = mid+1
 return lo
N,D,A=map(int,input().split())
lst=[0]*N
for i in range(N):
 lst[i]=list(map(int,input().split()))
lst.sort()
DMG=[0]*N
ans=0
for i in range(N):
 if i!=0:
  DMG[i]+=DMG[i-1]
 renji=nibun_right(lst,lst[i][0]+2*D)
 Z=max(int((lst[i][1]-1)/A)+1-DMG[i],0)
 DMG[i]+=Z
 if renji!=N:
  DMG[renji]-=Z
 ans+=Z
print(ans)