#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD=1000000007;
#define INF 1LL<<30
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()

int main() {
    ll l,r,m,k;
    cin>>l>>r>>m>>k;
    if((l*k-1+m)/m!=(r*k+m)/m) cout<<"Yes"<<endl;
    else cout<<"No"<<endl;

}