#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define sz(x) int(x.size())
using namespace std;
typedef long long ll;
typedef pair<int, int> P;

const ll INF = 1LL << 60;

ll A, B, C, D;
int main() {
    cin >> A >> B >> C >> D;

    for (int i = 1; i <= 100; i++) {
        if (i % 2 == 1) {
            // 高橋
            C -= B;
        } else {
            // 青木
            A -= D;
        }

        if (A <= 0) {
            cout << "No" << endl;
            break;
        }
        if (C <= 0) {
            cout << "Yes" << endl;
            return 0;
        }
    }
}