#include <bits/stdc++.h>

using namespace std;

int main() {
    double x, y;
    cin >> x >> y;
    x = x * 1000 / 3600;
    y = y * 1000 / 3600;

    int n;
    cin >> n;

    vector<int> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }

    int sum = a[0];
    double time = 0;
    for (int i = 0; i < n - 1; i++) {
        sum += a[i + 1];
        time += a[i] / x;
        if (y * time > sum) {
            cout << "NO" << endl;
            return 0;
        }
    }

    cout << "YES" << endl;

    return 0;
}