#include <bits/stdc++.h>

int main() {
  using namespace std;
  cin.tie(nullptr)->sync_with_stdio(false);
  int64_t a, b, c, d;
  cin >> a >> b >> c >> d;
  if (d * c - b > 0)
    cout << (a + d * c - b - 1) / (d * c - b) << '\n';
  else
    cout << "-1\n";
}

/**
*    author:  velengel
*    created: 24.04.2021 21:04:04
**/

#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; (i) < (int)(n); ++ (i))
using namespace std;
using ll = long long;
using P = pair<int, int>;
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b;return true;}return false;}

int main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int a,b,c;
  cin>>a>>b>>c;
  cout<<((a*a+b*b<c*c)?"Yes":"No")<<endl;

  return 0;
}