#include<bits/stdc++.h>
using namespace std;
long long a, b, c, d,t=0,x,y,k,z;
int main() {
cin >> a >> b >> c >> d;
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
freopen("countnum.inp","r",stdin);
freopen("countnum.out","w",stdout);
x = b / c - (a - 1) / c;
y = b / d - (a - 1) / d;
k = (c * d) / __gcd(c, d);
z = b / k - (a - 1) / k;
t= b - a + 1 - x - y + z;
cout << t;
}
{"html5":"htmlmixed","css":"css","javascript":"javascript","php":"php","python":"python","ruby":"ruby","lua":"text\/x-lua","bash":"text\/x-sh","go":"go","c":"text\/x-csrc","cpp":"text\/x-c++src","diff":"diff","latex":"stex","sql":"sql","xml":"xml","apl":"apl","asterisk":"asterisk","c_loadrunner":"text\/x-csrc","c_mac":"text\/x-csrc","coffeescript":"text\/x-coffeescript","csharp":"text\/x-csharp","d":"d","ecmascript":"javascript","erlang":"erlang","groovy":"text\/x-groovy","haskell":"text\/x-haskell","haxe":"text\/x-haxe","html4strict":"htmlmixed","java":"text\/x-java","java5":"text\/x-java","jquery":"javascript","mirc":"mirc","mysql":"sql","ocaml":"text\/x-ocaml","pascal":"text\/x-pascal","perl":"perl","perl6":"perl","plsql":"sql","properties":"text\/x-properties","q":"text\/x-q","scala":"scala","scheme":"text\/x-scheme","tcl":"text\/x-tcl","vb":"text\/x-vb","verilog":"text\/x-verilog","yaml":"text\/x-yaml","z80":"text\/x-z80"}
