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:
import heapq as hq

N, D, A = map(int,input().split())
m = []
for i in range(N):
    hq.heappush(m, tuple(map(int,input().split())))
ans = 0
dmg = 0; d = []
while m:
    X, H = m[0] # 
    if not d or (X <= d[0][0]):
        if dmg >= H:
            hq.heappop(m)
        else:
            k = (H - dmg + A - 1) // A
            ans += k
            dmg += k * A
            hq.heappush(d, (X + 2 * D, - k * A))
    else:
        dmg += d[0][1]
        hq.heappop(d)
    # print(dmg, m, d) #DB

print(ans)