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 collections import deque


def inpl():
    return list(map(int, input().split()))


N, D, A = inpl()
XH = [inpl() for i in range(N)]
XH.sort()
# print(XH)

bomb = [(h + A - 1) // A for x, h in XH]

ans = 0
dq = deque()
s_i = 0
sum_q = 0
for i in range(N):
    while dq and dq[0][1] < XH[i][0]:
        b, _ = dq.popleft()
        sum_q -= b

    bomb[i] -= sum_q
    if bomb[i] <= 0:
        pass
    else:
        ans += bomb[i]
        sum_q += bomb[i]
        dq.append([bomb[i], XH[i][0] + 2 * D])

print(ans)