/*
            _           __                _      _____ _____ _____ 
  ___ _   _| |__   ___ / _|_ __ ___  __ _| | __ |___  |___  |___  |
 / __| | | | '_ \ / _ \ |_| '__/ _ \/ _` | |/ /    / /   / /   / / 
| (__| |_| | |_) |  __/  _| | |  __/ (_| |   <    / /   / /   / /  
 \___|\__,_|_.__/ \___|_| |_|  \___|\__,_|_|\_\  /_/   /_/   /_/   

*/
#include<bits/stdc++.h>
using namespace std;
typedef long long ll ;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<ll> vi;
typedef vector<pll> vpll;
typedef unordered_map <ll,ll> umap ; 
//#pragma GCC optimize "trapv"
#define loop(i,a,b) for(ll i=a ;i<b;i++)
#define For(i,n) for(int i=0;i<(ll)n;i++)
#define Rev(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,n) for(int i=1;i<=n;++i)
#define F first
#define S second
#define pb push_back
#define em emplace_back
#define all(v) (v).begin(),(v).end()
#define mems(x, y) memset(x, y, sizeof(x))
#define sz(v) (v).size()
#define mp(a,b) make_pair(a,b)
#define pf(n) cout<<n<<"\n"
#define pff(n) cout << n << " " ; 
#define ar array
#define endl "\n" 
#define time        cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
long const M=1e9+7;
const long mxN =1e5+2 ;
const long mxNN =1e6+2 ;
void solve(){
    int a,b,c,d ;
    cin >> a >> b  >> c >> d ;
    for(int i=0;a>0&&c>0;i++){
        if(i&1)a-=d ;
        else c-=b ;
    }
    cout << (a>0?"Yes":"No")  << endl ;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    //cout << setprecision(20) << fixed ;
    solve() ;
    //ll t ; cin >> t ; while(t--)solve();
	return 0;
}
/*
            _           __                _      _____ _____ _____ 
  ___ _   _| |__   ___ / _|_ __ ___  __ _| | __ |___  |___  |___  |
 / __| | | | '_ \ / _ \ |_| '__/ _ \/ _` | |/ /    / /   / /   / / 
| (__| |_| | |_) |  __/  _| | |  __/ (_| |   <    / /   / /   / /  
 \___|\__,_|_.__/ \___|_| |_|  \___|\__,_|_|\_\  /_/   /_/   /_/   

*/
#include<bits/stdc++.h>
using namespace std;
typedef long long ll ;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<ll> vi;
typedef vector<pll> vpll;
typedef unordered_map <ll,ll> umap ; 
//#pragma GCC optimize "trapv"
#define loop(i,a,b) for(ll i=a ;i<b;i++)
#define For(i,n) for(int i=0;i<(ll)n;i++)
#define Rev(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,n) for(int i=1;i<=n;++i)
#define F first
#define S second
#define pb push_back
#define em emplace_back
#define all(v) (v).begin(),(v).end()
#define mems(x, y) memset(x, y, sizeof(x))
#define sz(v) (v).size()
#define mp(a,b) make_pair(a,b)
#define pf(n) cout<<n<<"\n"
#define pff(n) cout << n << " " ; 
#define ar array
#define endl "\n" 
#define time        cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
long const M=1e9+7;
const long mxN =1e5+2 ;
const long mxNN =1e6+2 ;
void solve(){
    int a,b,c,d ;
    cin >> a >> b  >> c >> d ;
    for(int i=0;a>0&&c>0;i++){
        if(i&1)a-=d ;
        else c-=b ;
    }
    cout << (a>0?"Yes":"No")  << endl ;
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    //cout << setprecision(20) << fixed ;
    solve() ;
    //ll t ; cin >> t ; while(t--)solve();
	return 0;
}
