#include<algorithm>
#include<cstring>
#include<string>
#include<cassert>
#include<cmath>
#include<climits>
#include<iomanip>
#include<stack>
#include<unordered_map>
#include<bitset>
#include<limits>
#include<complex>
#include<array>
#include <iostream>

using namespace std;
#define rep(i,m,n) for(int (i)=(int)(m);i<(int)(n);i++)
#define REP(i,n) rep(i,0,n)
#define ll long long

int main()
{
   ll l,r,m,k;
  cin >> l >> r >> m >> k;
  bool flag =false;
  ll a,b,c;
  a = k % m;
  b = l % m;
  c = r % m;
  
  if((k == 0) || (k*(r-l) >= m)) flag = true;
  else if((a*b % m) >= (a*c % m)) flag =true;
    
  if(flag) cout << "Yes" << endl;
    else cout << "No" << endl;
  
}