#include <bits/stdc++.h>

using namespace std;
using ll = long long;
using ii = pair<int, int>;

const int MAX { 200010 };
const ll MOD { 1000000007 }, oo { 1LL << 62 };

int solve(int N, const vector<int>& xs)
{
    return 0;
}

int main()
{
    ios::sync_with_stdio(false);

    int A, B, C, D;
    cin >> A >> B >> C >> D;

    int next = 0;

    while (A > 0 and C > 0)
    {
        switch (next) {
        case 0:
            C -= B;
            break;

        default:
            A -= D;
            break;
        }

        next = 1 - next;
    }

    cout << (next ? "Yes" : "No") << '\n';

    return 0;
}

