#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using Graph=vector<vector<pair<int,int>>>;
#define INF 1000000000000000000
#define MOD 1000000007

int main(){
  ll L,R,M,K;
  cin>>L>>R>>M>>K;
  if(K*R-K*L>=M){
    cout<<"Yes"<<endl;
  }else{
    ll left=K*L%M;
    ll right=K*R%M;
    if(right<left||left==0){
      cout<<"Yes"<<endl;
    }else{
      cout<<"No"<<endl;
    }
  }
}