//#define _GLIBCXX_DEBUG
#include<bits/stdc++.h>
#define PI 3.14159265359
using namespace std;
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
const long long INF= 1e+18+1;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll> >vvl;
typedef pair<ll,ll> P;
typedef tuple<ll,ll,ll> T;
const ll MOD=1000000007LL;
string abc="abcdefghijklmnopqrstuvwxyz";
string ABC="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
vl dx={-1,-1,-1,0,0,1,1,1};
vl dy={1,-1,0,1,-1,1,0,-1};

int main(){
  ll a,b,c,d;cin>>a>>b>>c>>d;
  if((a+d-1)/d>=(c+b-1)/b)cout<<"Yes"<<endl;
  else cout<<"No"<<endl;
}