#include <bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> ii;
typedef vector<int> vi;
typedef vector<ii> vii;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define in insert
#define sz(x) (int)x.size()
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define speed ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
const int INF = 1e18 + 5;
const int mod = 1e9 + 7;
const int  N = 2e5 + 314;
const long double pi = 3.1415926535897932384626433832795;
int bp(int pow, int n){
    int d = 1;
    while(n)
    {
        if(n%2==1)d=(d*pow)%mod;
        pow=(pow*pow)%mod;
        n/=2;
    }
    return d;
}
void solve(){
    int a, b, c, d;
    cin>>a>>b>>c>>d;
    int x = c, y = d;
    while (x>0&&y>0)
    {
        x-=d, y-=c;
    }
    if(x<=0)cout<<"No\n";
    else cout<<"Yes\n";
}
signed main(){
    speed;
    int t=1;
    //cin>>t;
    while(t--)solve();
}