#include<bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define int long long
int akaPow(int e, int p)
{
    int ans = 1;
    while (p > 0)
    {
        if (p & 1) ans = ans * e;
        e = e * e;
        p >>= 1;
    }
    return ans;
}
int32_t main() {
    IOS;
#ifndef ONLINE_JUDGE

    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int a, b, c;
    cin >> a >> b >> c;
    if (akaPow(a, 2) + akaPow(b, 2) < akaPow(c, 2)) cout << "Yes";
    else cout << "No";
}

#include<bits/stdc++.h>
#define f first
#define s second
#define pb push_back
#define M (L+R)/2
#define N 500009
#define inf 99999999999
#define ll long long
#define mod 1000000007
#define sz size();
using namespace std;


int main(){

	ios::sync_with_stdio(0);
	int V, T, S, D;
	
	cin>>V>>T>>S>>D;
	
	if(D>=T*V && D<=V*S){
		cout<<"No"<<endl;
	} else {
		cout<<"Yes"<<endl;
	}

	return 0;
}
