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

void solve(std::istream &in, std::ostream &out);

int main() {
#ifdef LOCAL
  freopen("../IO/b.in", "r", stdin);
//  freopen("../IO/b.in", "w", stdout);
#else
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  std::cout.tie(nullptr);
#endif
  solve(std::cin, std::cout);
  return 0;
}


void solve(std::istream &in, std::ostream &out) {
  int a, b, c, d;
  in >> a >> b >> c >> d;
  int z = 0;
  while (a > 0 && c > 0) {
    if (!z) c -= b;
    else a -= d;
    z ^= 1;
  }
  out << (z ? "Yes\n" : "No\n");
}
