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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <cstdlib>

#define FASTIO ios::sync_with_stdio(NULL); cin.tie(NULL);
#define show(x) cerr << #x << " = " << x << "\n"
#define mem( a , b ) memset( a , b , sizeof a )
#define popcnt(x) __builtin_popcount(x)
#define all(x) x.begin() , x.end()
#define SZ(a) (int)a.size()
#define ll  long long
#define ld  long double
#define vii vector  <ll>
#define dqi deque   <ll>
#define sii set     <ll>
#define vpi vector  <pii>
#define mii map     <ll,ll>
#define pii pair    <ll,ll>
#define vss vector  <string>
#define pb  push_back
#define F   first
#define S   second
#define L   length()
#define PI  3.141592654
#define OO (ll)1e18
using namespace std;
void ONLINE__JUDGE();

pii swapii( pii pr ){ return { pr.S , pr.F }; }
int dx[] = {  0 ,  0 , -1 , +1 , -1 , +1 , -1 , +1 };
int dy[] = { -1 , +1 ,  0 ,  0 , -1 , +1 , +1 , -1 };

const ll MOD = 1e9 + 7;
const ll MAX = 1e5 + 9;

ll a , b , c , d;

ll get( ll x , ll y , ll z )
{
    if ( z > y ) return 0;
    ll remX = x%z; ll xx = x-remX;
    if ( xx < x ) xx += z;

    ll remY = y%z; ll yy = y-remY;
    if ( yy > y ) yy -= z;

    ll n   = yy - xx + 1;
    ll ret = n/z + (bool)(n%z);
    return ret;
}

int main()
{
    FASTIO //ONLINE__JUDGE();

    cin >> a >> b >> c >> d;
  
    ll del = c*d / __gcd(c , d);
    cout << b - a + 1 - (get(a,b,c) + get(a,b,d) - get(a,b,del));
    return 0;
}

void ONLINE__JUDGE()
{
    #ifndef ONLINE_JUDGE
    freopen( "inp.c"         , "r" , stdin  );
    //freopen( "OutPut.txt"   , "w" , stdout );
    #endif // ONLINE_JUDGE
}