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 math import ceil
from bisect import bisect_right
n, d, a = (int(x) for x in input().split())
xh = []
for _ in range(n):
    x, h = (int(x) for x in input().split())
    xh.append([x, h])
xh = sorted(xh, key=lambda x: x[0])
cnt = 0
dmg = [0] * (n + 1)
for i, (x, h) in enumerate(xh):
    dmg[i] += dmg[i - 1]
    h -= dmg[i]
    if h <= 0:
        continue
    num = ceil(h / a)
    dmg[i] += num * a
    idx = bisect_right(xh, [x + 2 * d, float('inf')])
    dmg[idx] -= num * a
    cnt += num
print(cnt)