// Problem : B - Battle
// Contest : AtCoder - AtCoder Beginner Contest 164
// URL : https://atcoder.jp/contests/abc164/tasks/abc164_b
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

//S->----------------------------------------------------|
//R->--------------</AUTHOR - SRIJAN DE>-----------------|
//I->----</JALPAIGURI GOVERNMENT ENGINEERING COLLEGE>----|
//J->------------</INFORMATION TECHNOLOGY>---------------|
//A->-------------</sd2220@it.jgec.ac.in>----------------|
//N->----------------------------------------------------|
#include    <bits/stdc++.h>
#include    <ext/pb_ds/assoc_container.hpp>
using       namespace            std;
using       namespace            __gnu_pbds;
using       lli=                 long long ;
using       ull=                 unsigned long long ;
using       ld=                  long double;
#define     int                  long long
#define     mem(a,val)           memset( a,  val,  sizeof(a) )
#define     b_s                  binary_search
#define     u_b                  upper_bound
#define     l_b                  lower_bound
#define     nl                   cout<<endl
#define     pb                   push_back
#define     pf                   push_front
#define     ppb                  pop_back
#define     ppf                  pop_front
#define     in                   insert
#define     fi                   first
#define     se                   second
#define     pqueue               priority_queue
#define     rr                   return
#define     fr0(var,beg,end)     for(int var=beg;var<end;var++)
#define     fr1(var,end,beg)     for(int var=end-1;var>=beg;var--)
bool isprime(int n);
bool ispalin(int num);
bool isleapyear(int year);
int __lcm(int a, int b); 
int power(int x,int y);
int digitsum(int n);
int fact(int n);
int npr(int n, int r);
int ncr(int n, int r);
int evensum(int n);
int oddsum(int n);
void countSort(int arr[], int n, int exp);
void radixsort(int arr[], int n);
void print(int arr[], int n);
void sorts(string &str);
const int   MOD=                 (int)1e9 + 7;
const int   MOD1=                (int)1e9 + 9;
const int   MOD2=                998244353;
const ld    pi=                  atan2(0, -1);
const ld    eps=                 1e-9;
int         tests=               1;
template<class x,class y>x max(x a,y b){return (a>b)?a:b;}
template<class x,class y>x min(x a,y b){return (a<b)?a:b;}
template<class x,class y>x log(x n,y r){return (n>r-1)?1+log(n/r,r):0;}

int32_t main() 
{
	auto start = clock();
	ios_base::sync_with_stdio(0);
	cout.tie(0);
	cin.tie(0);	

//	cout<<fixed;
//	cout<<scientific;
//	cout<<fixed<<setprecision(12);
	// cin>>tests;
	for(int test=1;test<=tests;test++) 
	{
//		cout<<"Case #"<<test<<": ";

		
		int a,b,c,d;
		cin>>a>>b>>c>>d;
		
		for(int i=0;;i++)
		{
		    // cout<<a<<b<<c<<d<<endl;
		    if(a<=0)
		    {
		        cout<<"No";
		        return 0;
		    }
		    if(c<=0)
		    {
		        cout<<"Yes";
		        return 0;
		    }
		    if(i%2==0)
		    c-=b;
		    else
		    a-=d;
		    
		}
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
		
	}
	cerr<<endl<<endl<<endl<< "Time : " << double(clock() - start) / CLOCKS_PER_SEC <<endl;
	return 0;
}

































bool isprime(int n)
{
    bool prime[n + 1];
    memset( prime , true, sizeof(prime));
    for (int p = 2; p * p <= n; p++) {
        if (prime[p] == true) {
            for (int i = p * p; i <= n; i += p)
                prime[i] = false;
        }
    }
    if(n==1)
        return false;
    else if (prime[n])
        return true;
    else
        return false;
}
 
bool ispalin(int num)
{
    bool flag=false;
    int digit,rev=0,n=num;
    do
     {
         digit = num % 10;
         rev = (rev * 10) + digit;
         num = num / 10;
     } while (num != 0);
     if(rev==n)
     flag=true;
     return flag;
}
bool isleapyear(int year)  
{  
    if (year % 400 == 0)  
        return true;  
    
    if (year % 100 == 0)  
        return false;  
  
    if (year % 4 == 0)  
        return true;  
    return false;  
}  
int __lcm(int a, int b)  
{  
return (a*b)/__gcd(a, b);  
}
 
int power(int x,int y) 
{ 
	int temp; 
	if( y == 0) 
		return 1; 
	temp = pow(x, y/2); 
	if (y%2 == 0) 
		return temp*temp; 
	else
		return x*temp*temp; 
}
int digitsum(int n)
{
    int c=0;
    while(n>0)
    {
        c++;
        n/=10;
    }
    return c;
}
int fact(int n) 
{ 
    if (n <= 1) 
        return 1; 
    return n * fact(n - 1); 
}  
int ncr(int n, int r) 
{ 
    long long p = 1, k = 1; 
    if (n - r < r) 
        r = n - r; 
  
    if (r != 0) { 
        while (r) { 
            p *= n; 
            k *= r; 
            int m = __gcd(p, k); 
            p /= m; 
            k /= m; 
            n--; 
            r--; 
        } 
    } 
    else
        p = 1; 
    return p;
} 
int npr(int n, int r) 
{ 
    return fact(n) / fact(n - r); 
} 
int evensum(int n)
{
	return (n/2*(n/2+1));
}
int oddsum(int n)
{
	return (((n+1)/2)*((n+1)/2));
}
void countSort(int arr[], int n, int exp) 
{ 
	int output[n];
	int i, count[10] = {0}; 
	for (i = 0; i < n; i++) 
		count[ (arr[i]/exp)%10 ]++; 
	for (i = 1; i < 10; i++) 
		count[i] += count[i - 1]; 
	for (i = n - 1; i >= 0; i--) 
	{ 
		output[count[ (arr[i]/exp)%10 ] - 1] = arr[i]; 
		count[ (arr[i]/exp)%10 ]--; 
	} 
	for (i = 0; i < n; i++) 
		arr[i] = output[i]; 
} 
void radixsort(int arr[], int n) 
{
    int mx = arr[0]; 
	for (int i = 1; i < n; i++) 
		if (arr[i] > mx) 
			mx = arr[i];
	int m =mx;
	for (int exp = 1; m/exp > 0; exp *= 10) 
		countSort(arr, n, exp); 
} 
void print(int arr[], int n) 
{ 
    for (int i = 0; i < n; i++) 
        cout << arr[i] << " "; 
} 
void sorts(string &str)
{
	sort(str.begin(), str.end());
}


Measured memory_bytes: 3640