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

int main() {

int a,b,c,d;

cin >>a>>b>>c>>d;
string ans="Yes";
rep(i,1e9)
{
  if(i%2==0)
  {c-=b;}
  else
  {a-=d;}
  if(c<=0)
  {ans="Yes"; break;}
  if(a<=0)
  {ans="No"; break;}
  
}

cout << ans<<endl;




}
/*vector <int> a(3);
for (int i = 0; i < n; i++) {
    cin >> a.at(i);
  }*/