#include <bits/stdc++.h>
using namespace std;
int main()
{
	int a,b,c,d;
	cin>>a>>b>>c>>d;
	if (d>a*c||d<a*b)
	{
		cout<<"Yes"<<endl;
	}
	else
	{
		cout<<"No"<<endl;
	}
	return 0;
}
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vb = vector<bool>;
using vs = vector<string>;
using vvi = vector<vi>;
using vp = vector<pii>;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define sz(a) (int)((a).size())
#define all(a) (a).begin(), (a).end()
#define each(x, a) for (auto&& x : (a))
#define _overload3(_1, _2, _3, name, ...) name
#define rep1(n) rep2(_, n)
#define rep2(i, n) rep3(i, 0, n)
#define rep3(i, a, n) for (int i = (a), i##_len = (n); i < i##_len; ++i)
#define rep(...) _overload3(__VA_ARGS__, rep3, rep2, rep1)(__VA_ARGS__)
constexpr int inf = (1LL<<31) - 1;
constexpr int mod = 1e9 + 7;
constexpr double eps = 1e-10;
const double pi = acos(-1.0);
constexpr int dx[] = {1, 0, -1, 0};
constexpr int dy[] = {0, 1, 0, -1};
template<typename T> constexpr void print(const T& t) { cout << t << "\n"; }
template<typename T, typename U> constexpr bool chmax(T& a, const U& b) { if (a < b) a = b; return a < b; }
template<typename T, typename U> constexpr bool chmin(T& a, const U& b) { if (a > b) a = b; return a > b; }
template<typename T, typename U> istream& operator>>(istream& is, pair<T, U>& p) { is >> p.fi >> p.se; return is; }
template<typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) { os << p.fi << " " << p.se; return os; }
template<typename T> istream& operator>>(istream& is, vector<T>& v) { each(e, v) is >> e; return is; }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v) { each(e, v) os << e << " "; return os; }
struct Init { Init() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(10); }} init;

int main() {
    ll x, y, a, b;
    cin >> x >> y >> a >> b;
    ll cnt = 0;
    while ((double)a*x<=2e18 && a * x < y && x * a <= x + b) {
        x *= a;
        ++cnt;
    }
    cnt += (y - 1 - x) / b;
    print(cnt);
}