#include <bits/stdc++.h>
using namespace std;
#define rep(i, m, n) for(int i=m; i<n; i++)
typedef long long ll;
typedef pair<int, int> P;
typedef pair<ll, ll> Pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vll;
template <typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1;} return 0; }
template <typename T> bool chmin(T &a, const T &b) { if (a>b) { a=b; return 1;} return 0; }


int main() {
  int a,b,c,d; cin>>a>>b>>c>>d;
  int i=0;
  while(a>0&&c>0){
      if(i%2==0) c-=b;
      else a-=d;
      i++;
  }
  if(a<=0) cout<<"No"<<endl;
  else cout<<"Yes"<<endl;

}