#include <iostream>
#include <cstdio>
#include <set>
#include <list>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <string>
#include <sstream>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <cctype>
#include <cmath>
#include <fstream>
#include <iomanip>
//#include <unordered_map>
using namespace std;
#define dbg(x) cerr << #x " = " << x << endl;
typedef pair<int, int> P;
typedef long long ll;

int main()
{
    //freopen("in.txt", "r", stdin);
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int a,b,c,d;
    cin >> a >> b >> c>> d;
    int ta = a / d;
    if(a % d) ta++;
    int tb = c / b;
    if(c % b) tb++;
    if(tb <= ta)
    {
        cout << "Yes" << endl;
    }
    else
    {
        cout << "No" << endl;
    }
    
}