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>

int yakusu(int a, int b) {
	int tmp, r;

	if (a<b) {
		tmp = a;
		a = b;
		b = tmp;
	}

	r = a % b;
	while (r != 0) {
		a = b;
		b = r;
		r = a % b;
	}

	return b;
}

int main() {
	long long int A, B, C, D, bc, bd, bcd, CD, x, y, Bkosu, Akosu, ac, ad, acd;

	scanf("%lld %lld %lld %lld", &A, &B, &C, &D);

	CD = C * D;
	x = yakusu(C, D);
	y = CD / x;

	bc = B / C;
	bd = B / D;
	bcd = B / y;
	Bkosu = B - (bc + bd - bcd);

	ac = (A - 1) / C;
	ad = (A - 1) / D;
	acd = (A - 1) / y;
	Akosu = (A - 1) - (ac + ad - acd);

	printf("%lld", Bkosu - Akosu);

	return 0;
}