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:
def main():
    import sys
    from bisect import bisect
    from operator import itemgetter
    b=sys.stdin.buffer
    n,d,a=map(int,b.readline().split())
    m=map(int,b.read().split())
    c=[0]*(n+1)
    z=sorted(zip(m,m),key=itemgetter(0))
    y=[x for x,_ in z]
    s=b=0
    for i,(x,h)in enumerate(z):
        c[i]+=b
        b=c[i]
        h-=b
        t=-h//a
        if t<0:
            b-=t*a
            c[bisect(y,x+d+d)]+=t*a
            s-=t
    print(s)
main()