#include<iostream>
signed main(){
  int64_t l,r,m,k;
  std::cin>>l>>r>>m>>k;
  int64_t kl = k*l;
  int64_t kr = k*r;
  std::cout<< (kl<=(kl/m+1)*m&&(kl/m+1)*m<=kr?"Yes":"No") <<std::endl;
}