/*
    
*/
#include<bits/stdc++.h>
using namespace std;
#define CoDeFoRcEs_and_ChIlL ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
typedef long long ll;
#define fl(i,a,b) for(ll i=a;i<b;i++)
#define rfl(i,a,b) for(ll i=a;i>b;i--)
#define pb push_back
#define mp make_pair
#define test ll t;cin>>t;while(t--)
#define lld long double
#define vpp vector<pair<ll,ll>>
#define pii pair<ll,ll>
#define ff first
#define ss second
#define endl '\n'
#define trace(x) cerr<<#x<<": "<<x<<" "<<endl;
const ll M =1000000007;
const double pi  =acos(-1);
const int N = 2e5 + 10;
int main()
{  
    CoDeFoRcEs_and_ChIlL;
    ll a,b,c,d,i=0;
    cin>>a>>b>>c>>d;
    if(a/d >= c/b) cout << "Yes";
	else cout << "No";
} 