//bestesebsesebsebstbtbtsebt
#include<bits/stdc++.h>
using namespace std;
const int N = 1e2 + 5;
int l,r,a,b;
int lcm(int a,int b) {
    return (a/__gcd(a, b))*b;
    }
int main(){
     ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
     freopen("countnum.inp","r",stdin);
     freopen("countnum.out","w",stdout);
     cin>>l>>r>>a>>b;
    int t = lcm(a, b);
    int ba = (r / a) - ((l-1) / a);
    int bb = (r / b) - ((l-1) / b);
    int bo = (r / t) - ((l-1) / t);
    cout<< (r-l+1)-(ba+bb-bo);
}