Problem:
Score : 300 points

Problem Statement

You are given four integers A, B, C, and D. Find the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Constraints

1\leq A\leq B\leq 10^{18}

1\leq C,D\leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

A B C D

Output

Print the number of integers between A and B (inclusive) that can be evenly divided by neither C nor D.

Sample Input 1

4 9 2 3

Sample Output 1

2

5 and 7 satisfy the condition.

Sample Input 2

10 40 6 8

Sample Output 2

23

Sample Input 3

314159265358979323 846264338327950288 419716939 937510582

Sample Output 3

532105071133627368

Solution in C (GCC 5.4.1) (judge verdict: Runtime Error)

#include <stdio.h>

int main(void){
  unsigned long long a,b,c,d,r,lcm,x,tmp,ans;
  unsigned long long sum=0;
  scanf("%lld %lld %lld %lld",&a,&b,&c,&d);
  sum += (b/c) - ((a-1)/c);
  sum += (b/d) - ((a-1)/d);
  x = c*d;
  if(c<d){
    tmp = c;
    c = d;
    d = tmp;
  }
  r = c % d;
  while(r!=0){
    c = d;
    d = r;
    r = c % d;
  }
  lcm = x/r;
  sum -= (b/lcm) - ((a-1)/lcm);
  ans = (b-a+1) - sum;
  printf("%lld\n",ans);
  return 0;
}