#include <iostream>
using namespace std;
#define LL long long

int main()
{
    int taka_tai, taka_kou, ao_tai, ao_kou;
    cin >> taka_tai >> taka_kou >> ao_tai >> ao_kou;

    while (true) {
        ao_tai -= taka_kou;
        if (ao_tai <= 0) {
            cout << "Yes" << endl;
            break;
        }

        taka_tai -= ao_kou;
        if (taka_tai <= 0) {
            cout << "No" << endl;
            break;
        }

    }

    return 0;
}

