/*
********************
Author : MIHIR ARORA
********************
*/
#include <bits/stdc++.h>
using namespace std;
#define fast cin.tie(NULL); cout.tie(NULL); 
#define input int n; scanf("%d",&n); int*arr = new int[n];  for(int i=0;i<n;i++) scanf("%d",&arr[i]);  
#define inputs int n; scanf("%d",&n); char str[n];   cin>>str;   

typedef long long int ll;
const int mod=1e9+7; 
ll add(ll a, ll b)
{
    return (a%mod+b%mod)%mod;
}

ll mul(ll a, ll b)
{
    return ((a%mod)*(b%mod))%mod;
}

ll sub(ll a, ll b)
{
    return ((a%mod) - (b%mod))%mod;
}
inline void solve()
{
 input; 
}
int main()
{ 
    fast; 
   int a,b,c,d; 
    cin>>a>>b>>c>>d; 
    int ctr=1; 
    while(a>0 && c>0)
    {
        if(ctr%2==0)
        {
            a=a-d; 
        
        }
        else
        {
            c=c-b; 
         
        }
        ctr++; 
    }
    
    if(c<=0)
        cout<<"Yes"; 
    else if(a<=0)
        cout<<"No"; 
}