#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define lvector vector<ll>
#define lque queue<ll>
#define lpque priority_queue<ll>
#define dlpque priority_queue<ll,lvector,greater<ll>>
#define P pair<ll,ll>
#define ALL(a) (a).begin(),(a).end()
#define rep(i,n) for(ll (i)=0; (i)<(n); ++(i))
#define print(a) cout << (a) << endl

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  ll a,b,c,d,cnt=0;cin>>a>>b>>c>>d;
  while(a>0&&c>0) {
    if(cnt%2==0) c-=b;
    else a-=d;
    cnt++;
  } 
  puts((a>0)?"Yes":"No");
  return 0;
}