#include <bits/stdc++.h>
using namespace std;
#define ll long long int
#define vi vector<int>
#define vll vector<ll>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vpii vector<pii>
#define pb push_back
#define MOD 1000000007
#define all(x) x.begin(), x.end()
#define sze(x) (int) x.size()

int main() {

    double v, s, t, d;
    scanf("%lf %lf %lf %lf", &v, &s, &t, &d);

    if(d/v < s || d/v > t) {
        printf("Yes\n");
    }
    else {
        printf("No\n");
    }
}


#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main() {
 double a,b,c,d;
 cin >> a >> b >> c >> d;
 double k = (a*d+b*c)/(b+d);
 cout << setprecision(8) << k << endl;
}