#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
typedef long long ll;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#define ios ios_base::sync_with_stdio(0) ; cin.tie(0) ; cout.tie(0)
#define so sizeof
#define pb push_back
#define cl clear() ;
#define vl vector<ll>
#define sz size()
#define len length()
#define emp empty()
#define el endl;cout.flush()
#define be begin()
#define fi first
#define se second
#define br break
#define en end()
#define ro return 0
#define br break
#define eb emplace_back
#define con continue
#define ms(x) memset(x , 0, so x)
#define all(x) (x).be , (x).en
#define acc(x) accumulate((x).be , (x).en , 0ll)
#define forn(i,a,b) for(ll i=a;i<=b;++i)
#define rng_58 mt19937 rng(chrono::steady_clock::now().time_since_epoch().count())
#define vll vector<pair<ll,ll> >
#define pll pair<ll,ll>
#define plll pair<ll,pair<ll,ll>>
#define plvl pair<pair<ll,ll> ,ll>
#define mp make_pair
#define trace3(a,b,c) cerr <<"a is " << a << " b is " << b << " c is " << c << el;
#define trace4(a,b,c,d) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << el ;
#define trace5(a,b,c,d,e) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << " e is " << e << el;
#define trace6(a,b,c,d,e,f) cerr <<"a is " << a << " b is " << b << " c is " << c <<" d is " << d << " e is " << e << " f is " << f << el ;
ll lcm(ll c , ll d){
   return (c * d ) / __gcd(c , d) ;
}
int main()
{
    ios;
    ll a , b , c , d ;
    cin >> a >> b >> c >> d;
    ll tot = b - a + 1 ;
    ll e = lcm(c , d);
    ll ans = 0;
    ll fbc = -1;
    if(a % c == 0){
        fbc = a ;
    }
    else {
        ll rem = a % c ;
        ll foo = a - rem ;
        ll to = foo + c ;
        fbc = to ;
    }
    if(fbc == -1) throw ;
    ll lbc = -1 ;
    if(b % c == 0){
        lbc = b ;
    }
    else {
        ll rem = b % c ;
        lbc = b - rem ;
    }
    if(lbc  == -1) throw ;
    ll fbd = -1 ;
    if(a % d == 0){
        fbd = a ;
    }
    else {
        ll rem = a % d ;
        ll foo = a - rem ;
        ll to = foo + d ;
        fbd = to ;
    }
    if(fbd == -1) throw ;
    ll lbd = -1 ;
    if(b % d == 0 ){
        lbd = b ;
    }
    else {
        ll rem = b % d ;
        lbd = b - rem ;
    }
    if(lbd == -1) throw ;
    ll fbe = -1 ;
    if(a % e == 0 ){
        fbe = a ;
    }
    else {
        ll rem = a % e ;
        ll foo = a - rem ;
        ll to = foo + e ;
        fbe = to ;
    }
    if(fbe == -1) throw ;
    ll lbe = -1 ;
    if(b % e == 0){
        lbe = b ;
    }
    else {
        ll rem = b % e ;
        lbe = b - rem ;
    }
    if(lbe == -1) throw ;
    ans = 0 ;
    ///trace6(fbc , lbc , fbd , lbd , fbe , lbe);
    if(fbc <= lbc){
        ll hii = (lbc - fbc) / c ;
        ++hii;
        ans = ans + hii ;
    }
    if(fbd <= lbd){
        ll hii = (lbd - fbd) / d ;
        ++hii;
        ans = ans + hii;
    }
    if(fbe <= lbe){
        ll hii = (lbe - fbe) / e ;
        ++hii ;
        ans = ans - hii ;
    }
    ll zizz = tot - ans ;
    cout << zizz << el ;
}































Measured memory_bytes: 256