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 long int gcd(long long int x,long long int y)
{
	if(x<y)return gcd(y,x);
	else return ((x%y==0) ? y : gcd(y,x%y));
}


int main()
{
	long long int a,b,c,d,g,lcm;
	long long int n,m,o=0;
	//nは[a,b]区間中のcで割り切れる整数の個数
	//mは[a,b]区間中のdで割り切れる整数の個数
	
	scanf("%lld %lld %lld %lld",&a,&b,&c,&d);
	a--;
	g=gcd(c,d);
	n=(b/c)-(a/c);
	m=(b/d)-(a/d);
	
	lcm=c*d/g;
	o=(b/lcm)-(a/lcm);
	
	//printf("%lld,%lld,%lld,%lld\n",lcm,n,m,o);
	printf("%lld",((b-a)-n-m+o));
	return 0;
}