#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define ff first
#define ss second

void io(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    #ifdef LOCAL
        freopen("input.txt","r",stdin);
        freopen("output.txt","w",stdout);
    #endif
}
auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
mt19937_64 mt(seed);
#ifdef LOCAL
    #include "debug.h"
#else
    #define debug(...) 42
#endif

const int N = 2e3 + 50;
const int mod = 998244353 ;

int main(){
    io();

    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int odd = 0;
    while(1) {
        odd = odd ^ 1;
        if(odd & 1) {
            c -= b;
        }
        else {
            a -= d;
        }

        if(c <= 0) {
            cout << "Yes";
            return 0;
        }
        if(a <= 0) {
            cout << "No";
            return 0;
        }
    }

}

