import java.util.*;

public class Main {


    public static long lcm(long m, long n){
        return m*n/gcd(m,n);
    }

    public static long gcd(long c, long d){
        if (c<d){return gcd(d,c);}
        if(d==0){return c;}
        return gcd(d, c%d);
    }


    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        long a = sc.nextLong();
        long b = sc.nextLong();
        long c = sc.nextLong();
        long d = sc.nextLong();

//        long num[] = new long[b-a+1];
//        for (long i=0; i<b-a+1; i++){
//            num[i] = a+i;
//        }

        long count=0;

//        long total = b-a+1;


//        b = b-(b/c)-(b/d)+b/lcm(c,d);
//        a = a-1-((a-1)/c)-((a-1)/d)+(a-1)/lcm(c,d);

//        count = b-a;

        long c_count=0;
        long d_count=0;
        long cd_count=0;

        c_count = b/c-(a-1)/c;
        d_count = b/d-(a-1)/d;
        cd_count = b/lcm(c,d)-(a-1)/lcm(c,d);
//
//
//        c_count = b/c - (a-1)/c;
//        d_count = b/d - (a-1)/d;
//        cd_count = b/lcm(c,d)-(a-1)/lcm(c,d);
//
//        if (((c-(a%c))+b%c)>c){
//            c_count += (b-a+1)/c-1;
//        }else{
//            c_count += (b-a+1)/c;
//        }
//
//
//        if (((d-(a%d))+b%d)>d){
//            d_count += (b-a+1)/d-1;
//        }else{
//            d_count += (b-a+1)/d;
//        }
//
//
//
//
//        if (((lcm(c,d)-(a%lcm(c,d))+b%lcm(c,d))>lcm(c,d))){
//            cd_count += (b-a+1)/lcm(c,d)-1;
//        }else{
//            cd_count += (b-a+1)/lcm(c,d);
//        }

        count = (b-a+1)-c_count-d_count+cd_count;

        System.out.println(count);

    }
}


/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz