#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < n; i++)
#define per(i,n) for(int i = n-1; i >= 0; i--)
typedef long long ll;
typedef pair<int, int> P;
typedef pair<long long, long long> Pll;
typedef vector<int> vi;
typedef vector<ll> vll;

int main() {
  int a, b, c, d;
  cin >> a >> b >> c >> d;
  int p = a/b;
  if(a%b!=0) p++;
  int q = c/d;
  if(c%d!=0) q++;
  if(p<=q) cout << "No" << endl;
  else cout << "Yes" << endl;
  return 0;
}