#include <bits/stdc++.h>
#define rep(i,a,b) for(ll i=ll(a);i<ll(b);i++)
#define irep(i,a,b) for(ll i=ll(a);i>=ll(b);i--)
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
#define pb push_back
#define mp make_pair
#define F .first
#define S .second 
using ll=long long;
using ld=long double;
const ll INF = 1LL<<60;
const ll mod=1e9+7;
using namespace std;
ll GCD(ll a, ll b) { return b ? GCD(b, a%b) : a; }

int main(){
    ll a,b,c,d;
    cin>>a>>b>>c>>d;
    ll aa=ceil((ld)a/d);
    ll bb=ceil((ld)c/b);
    if(aa==bb)cout<<"Yes";
    else if(aa>bb)cout<<"Yes";
    else cout<<"No";
    
}
