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: Accepted)

#include <stdio.h>

long GCD(long a, long b){
  long dividend, divisor;
  if (a >= b) {
    dividend = a;
    divisor = b;
  } else {
    dividend = b;
    divisor = a;
  }
  long remainder;
  while (1) {
    if (divisor == 1) {
      return 1;
    }
    remainder = dividend % divisor;
    if (remainder == 0) {
      break;
    } else {
      dividend = divisor;
      divisor = remainder;
    }
  }
  return divisor;
}

int main(void){

  long a,b,c,d;
  scanf("%ld %ld %ld %ld", &a, &b, &c, &d);

	long lcm = c*d/GCD(c,d);
	long all = b-b/c-b/d+b/lcm;
	a--;
	long minus = a-a/c-a/d+a/lcm;
	long answer = all - minus;

	printf("%ld\n", answer);

  return 0;
}