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 = []
X = []

for i in range(N):
    x,h = map(int,input().split())
    XH.append([x,h,0])
    X.append(x)
    
XH.sort(key = lambda a:a[0])
XH.append([float('inf'),0,0])
X.sort()
X.append(float('inf'))

import bisect
ans = 0

for i in range(N):
    x,h,k = XH[i]
    dk = max(-(-(h-k*A)//A),0)
    #print(x,h,k,dk)
    ans += dk
    
    XH[i][2] += dk
    j = bisect.bisect_right(X,x+2*D)
    XH[j][2] -= dk

    XH[i+1][2] += XH[i][2]
    
print(ans)