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
import bisect


N, D, A = map(int, input().split())
L = [list(map(int, input().split())) for _ in range(N)]
L = [[pos, ceil(hp/A)] for pos, hp in L]
L = sorted(L, key=lambda pos: pos[0])

POS = [v[0] for v in L]
ES = [0]*(N+1)
ans, c = 0, 0
for i in range(N):
    c -= ES[i]
    if L[i][1] > c:
        t = L[i][1]-c
        ans += t
        c += t
        ES[bisect.bisect_right(POS, POS[i]+2*D)] += t
print(ans)