#include<bits/stdc++.h>
    using namespace std;


    //Optimisations

    #pragma GCC target ("avx2")
    #pragma GCC optimization ("unroll-loops")
    #pragma GCC optimize("O2")


    //shortcuts for functions

    #define pb push_back
    #define mp make_pair
    #define ff first 
    #define ss second
    #define endl "\n"
    #define all(v) v.begin(),v.end()
    #define rall(v) v.rbegin(),v.rend()
    #define th(n) cout<<n<<endl
    #define gc getchar_unlocked
    #define ms(s, n) memset(s, n, sizeof(s))
    #define prec(n) fixed<<setprecision(n)
    #define n_l '\n'


    // make it python 

    #define gcd __gcd
    #define append push_back
    #define str to_string
    #define upper(s) transform(s.begin(),s.end(),s.begin(),::toupper)
    #define lower(s) transform(s.begin(),s.end(),s.begin(),::tolower)
    #define print(arr) for(auto el: arr) cout<<el<<" ";cout<<endl



    // utility functions shortcuts

    #define max3(a,b,c) max(a,max(b,c))
    #define min3(a,b,c) min(a,min(b,c))
    #define sswap(a,b) {a=a^b;b=a^b;a=a^b;}
    #define swap(a,b) {auto temp=a; a=b; b=temp;}
    #define init(dp) memset(dp,-1,sizeof(dp));
    #define set0(dp) memset(dp,0,sizeof(dp));
    #define bits(x) __builtin_popcount(x)
    #define SORT(v) sort(all(v))
    #define endl "\n"
    #define forr(i,n) for(ll i=0;i<n;i++)
    #define formatrix(i,n) for(ll i=0;i<n;i++, cout<<"\n")
    #define eof (scanf("%d" ,&n))!=EOF




    // declaration shortcuts

    #define vi vector<int>
    #define vll vector<ll>
    #define vvi vector<vector<int>>
    #define vvl vector<vector<ll>> 
    #define pll pair<ll,ll>
    #define ppl pair<ll,pp>
    #define ull unsigned long long
    #define ll long long
    #define mll map< ll, ll > 
    #define sll set< ll > 
    #define uni(v)     v.erase(unique(v.begin(),v.end()),v.end());
    #define ini(a, v)       memset(a, v, sizeof(a))



    // Constants

    constexpr int dx[] = {-1, 0, 1, 0, 1, 1, -1, -1};
    constexpr int dy[] = {0, -1, 0, 1, 1, -1, 1, -1};
    constexpr ll INF = 1999999999999999997; 
    constexpr int inf= INT_MAX;
    constexpr int MAXSIZE = int(1e6)+5;
    constexpr auto PI  = 3.14159265358979323846L;
    constexpr auto oo  = numeric_limits<int>::max() / 2 - 2;
    constexpr auto eps = 1e-6;
    constexpr auto mod = 1000000007;
    constexpr auto MOD = 1000000007;
    constexpr auto MOD9 = 1000000009;

    // Debugging 

    // For reference: https://codeforces.com/blog/entry/65311

    #define dbg(...) cout << "[" << #__VA_ARGS__ << "]: "; cout << to_string(__VA_ARGS__) << endl
    template <typename T, size_t N> int SIZE(const T (&t)[N]){ return N; } template<typename T> int SIZE(const T &t){ return t.size(); } string to_string(string s, int x1=0, int x2=1e9){ return '"' + ((x1 < s.size()) ? s.substr(x1, x2-x1+1) : "") + '"'; } string to_string(const char* s) { return to_string((string) s); } string to_string(bool b) { return (b ? "true" : "false"); } string to_string(char c){ return string({c}); } template<size_t N> string to_string(bitset<N> &b, int x1=0, int x2=1e9){ string t = ""; for(int __iii__ = min(x1,SIZE(b)),  __jjj__ = min(x2, SIZE(b)-1); __iii__ <= __jjj__; ++__iii__){ t += b[__iii__] + '0'; } return '"' + t + '"'; } template <typename A, typename... C> string to_string(A (&v), int x1=0, int x2=1e9, C... coords); int l_v_l_v_l = 0, t_a_b_s = 0; template <typename A, typename B> string to_string(pair<A, B> &p) { l_v_l_v_l++; string res = "(" + to_string(p.first) + ", " + to_string(p.second) + ")"; l_v_l_v_l--; return res; } template <typename A, typename... C> string to_string(A (&v), int x1, int x2, C... coords) { int rnk = rank<A>::value; string tab(t_a_b_s, ' '); string res = ""; bool first = true; if(l_v_l_v_l == 0) res += n_l; res += tab + "["; x1 = min(x1, SIZE(v)), x2 = min(x2, SIZE(v)); auto l = begin(v); advance(l, x1); auto r = l; advance(r, (x2-x1) + (x2 < SIZE(v))); for (auto e = l; e != r; e = next(e)) { if (!first) { res += ", "; } first = false; l_v_l_v_l++; if(e != l){ if(rnk > 1) { res += n_l; t_a_b_s = l_v_l_v_l; }; } else{ t_a_b_s = 0; } res += to_string(*e, coords...); l_v_l_v_l--; } res += "]"; if(l_v_l_v_l == 0) res += n_l; return res; } void dbgs(){;} template<typename Heads, typename... Tails> void dbgs(Heads H, Tails... T){ cout << to_string(H) << " | "; dbgs(T...); }

    #define dbgm(...) cout << "[" << #__VA_ARGS__ << "]: "; dbgs(__VA_ARGS__); cout << endl;
    #define n_l '\n'


    int main()
    {
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout.tie(NULL);
        ll a,b,c,d,ans , lcm;
        cin>>a>>b>>c>>d;
        lcm = ((c*d)/__gcd(c,d));
        a--;
        ans =  (b/c) - (a/c) + (b/d) - (a/d) - (b/lcm) + (a/lcm);
        a++;
        ans = b - a + 1 - ans;
        th(ans);
    }


Measured memory_bytes: 256