#include<bits/stdc++.h>

using namespace std;
#define ll  long long
#define ld  long double
#define endl '\n'
#define FAST ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
const ll MOD = 1e9 + 7;
const double PI = 3.141592653589793238463;
const int MAXN = 3e5 + 5;


    void debug_out() {
    cerr << endl;
}

template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << H;
    debug_out(T...);
}

#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)

int main() {
    FAST
   int h1,s1,h2,s2;
    cin>>h1>>s1>>h2>>s2;
    int c=0;
    while(h1>0 && h2>0)
    {
        if(c%2==0)
        h2-=s1;
        else
            h1-=s2;
        c++;
    }
    if(h2<=0)
        cout<<"Yes"<<endl;
    else
        cout<<"No"<<endl;
    return 0;
}