#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define set_bits(a) __builtin_popcount(a)
#define pb push_back
#define pf push_front
#define mod 1000000007
#define M 998244353
#define fi first
#define se second
#define endl '\n'
#define INF 1e18
#define PI 3.14159265358979323846
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);


int main()
{
     ll ha,sa,hb,sb;
     cin>>ha>>sa>>hb>>sb;
     ll flag=0;

     while(1)
     {
         hb-=sa;
         if(hb<=0)
         {
             break;
         }
         ha-=sb;
         if(ha<=0)
         {
             flag=1;
             break;
         }
     }
     if(flag)
     {
         cout<<"No"<<endl;
     }
     else
     {
         cout<<"Yes"<<endl;
     }
}
