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())
XH=[list(map(int, input().split())) for _ in range(N)]

XH.sort()

B=0
Bt=[0]*N
Bx=[0]*N
l=0
r=-1

ans=0
for i in range(N):
    x,h = XH[i]
    if h<=0: continue
    #今までの爆弾ダメージを計算
    while l<=r:
        if Bx[l]<x: #もう届かない
            B-=Bt[l]*A
            l+=1
        else: #まだ届く
            break
    h-=B
    if h>0:
        t=(h+A-1)//A #ここで爆弾を使う回数
        ans+=t
        r+=1
        Bt[r]=t
        Bx[r]=x+(2*D)
        B+=A*t

print(ans)