#include <bits/stdc++.h>

using namespace std;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int X, Y, N;
  cin >> X >> Y >> N;
  vector<int> A(N);
  for (auto&& e : A) {
    cin >> e;
  }
  vector<double> B(N + 1, 0);
  for (int i = 0; i < N; i++) {
    B[i] += A[i];
    B[i + 1] += B[i];
  }
  for (int i = 0; i < N - 1; i++) {
    double t = B[i] / X;
    if (B[i + 1] < Y * t) {
      cout << "NO" << '\n';
      return 0;
    }
  }
  cout << "YES" << '\n';
  return 0;
}