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>
#include<stdlib.h>
#include<math.h>
#include<string.h>
void swap(long long *x,long long *y){
    long long tmp;
    tmp=*x;
    *x=*y;
    *y=tmp;
}
int main(void){
    long long A,B,C,D;
    scanf("%lld %lld %lld %lld",&A,&B,&C,&D);
    long long C2=C,D2=D;
    long long missC=0,missD=0,missCD=0;
    long long a=C2*D2;
    if(C2<D2){
        swap(&C2,&D2);
    }
    long long r=C2%D2;
    while(r!=0){
        C2=D2;
        D2=r;
        r=C2%D2;
    }
    long long MCM=a/D2;
   // printf("MCM=%lld:",MCM);
    missC=B/C-(A-1)/C;
    missD=B/D-(A-1)/D;
    missCD=B/MCM-(A-1)/MCM;
    //printf("missC=%lld:missD=%lld:missCD=%lld\n",missC,missD,missCD);
    long long count=(B-A+1)-missC-missD+missCD;
    printf("%lld",count);
    return 0;

}