/*
 Abu Jafor Mohammad Saleh
 ios_base :: sync_with_stdio(false);
 cin.tie(NULL);
 */

#include<cstdio>
#include<iomanip>
#include<sstream>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<algorithm>
#include<set>
#include<queue>
#include<deque>
#include<stack>
#include<list>
#include<iostream>
#include<fstream>
#include<numeric>
#include<string>
#include<vector>
#include<cstring>
#include<map>
#include<iterator>
#include<limits>
#include <algorithm>
#include <unordered_map>
#include<fstream>
#define f first
#define s second
#define MOD 1000000007

#define INF (int)1e9
#define PI 3.1415926535897932384626433832795
#define BOUNDARY(i, j) ((i >= 0 && i < rows) && (j >= 0 && j < coloums))

//#include<bits/stdc++.h>
#define fast ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define ll long long
const ll maxn = 2*100005;
using namespace std;
int X[] = {0, 1, 0, -1};
int Y[] = {-1, 0, 1, 0};
int rows,coloums;
long long  gcd(long long  a, long long b)
{
    if (b == 0)
        return a;
    return gcd(b, a % b);
}

int main(){
    fast;
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    
    while(1)
    {
        c = c-b;
        if (c<=0){
            cout<<"Yes"<<endl;
            break;
        }
        a = a-d;
        if(a<=0){
            cout<<"No"<<endl;
            break;
        }
    }
}
